Spontaneously Generating Fish

In a previous blogpost I discussed how the Swiss scholar Conrad Gessner (1516-1565) describes two strange species of fish, which generate spontaneously. Previously I identified these species as the sprat and the Baltic herring. In this blogpost I explore the background of Gessner’s assumptions about the spontaneous generation of fish.


The Reproduction of Fish

In his 1558 book on fish Historia Piscium Conrad Gessner describes the membras, which I identified as the Baltic herring in my last blog post:

‘Aristotle writes that the membras comes from the aphya phalerica.’

This is confirmed in his description of the aphya phalerica, which was identified as the sprat:

‘The aphya phalerica is mentioned by Aristotle, and it is confirmed the membras comes from this. I believe that the aphya phalerica generates spontaneously’

This tells us that the author believes these fishes to generate spontaneously, which seems somewhat surprising. The study of fish was a booming topic in Gessner’s day, from around 1550 renowned scholars produced one publication on fish after the other. All of these experts agreed that fish reproduce sexually. In fact, Gessner described this reproduction process in detail. He makes an exception however, for these two as well as a handful of other species. Why does he do this?


Fig. 1 Gessner’s sprat, or aphya phalerica. Historia Piscium. Zurich, Froschauer, 1558.


Spontaneous Generation

A belief in spontaneous generation, the coming into existence of living beings not from parents but through some other means, originates in the classical era and was still widely accepted within the scholarly community in the sixteenth century. Small creatures, such as for example insects, were thought to generate spontaneously. Some base material was needed for this, often dirt, mud, or decaying matter. From this material a living creature would form spontaneously. As Gessner indicates in his descriptions, we can trace such ideas back to Aristotle’s History of Animals. Aristotle combined information obtained from a variety of sources, resulting in an overview of ideas commonly accepted in the classical era. One such idea was spontaneous generation. While, like Gessner, Aristotle acknowledges that most fish reproduce sexually, he believed that some were the result of spontaneous generation.

Discussing fish, in book VI, part 15, of his History of Animals, Aristotle states:

“Such fish as are neither oviparous nor viviparous arise all from one of two sources, from mud, or from sand and from decayed matter that rises thence as scum”


Fig. 2 Spontaneous generation. Clipart Library 


Empirical Evidence?

Aristotle’s ideas were absorbed into Mediaeval, and later into Renaissance science. The idea that animals sometimes generated spontaneously remained more or less unchallenged, and often even seemed to be confirmed by experience. For example, a century after Gessner published his work, the Dutch artist Johannes Goedaert (1617-1668) left out a cup of his own urine and watched it over a period of time. Eventually flies emerged from the cup and, not having noticed the fly that must have laid its eggs near this rich source of nutrients, he took this to prove spontaneous generation. Goedaert would later change his mind but for a while found this experiment quite convincing. Similarly, a little before Goedaert conducted his experiment, Jan Baptist van Helmont (1580-1644) felt confident to provide the following recipe for mice: Place a dirty shirt or some rags in an open pot or barrel containing a few grains of wheat or some wheat bran, and in 21 days, mice will appear.


Fig. 3 Where there is grain, there are mice. A Video (17/ 6/ 2016), Little mouse in barrel with wheat. Retrieved from youtube.com.


This illustrates perfectly why the concept of spontaneous generation proved so durable, our own observations often seem to confirm it. We can conclude from Aristotle’s History of Animals that the same sort of confusing experience appeared to confirm the concept in antiquity. Aristotle backs up his claim that certain fish can generate spontaneously by citing observations that others have shared with him.

“As a proof that these fish occasionally come out of the ground we have the fact that in cold weather they are not caught, and that they are caught in warm weather, obviously coming up out of the ground to catch the heat; also when the fishermen use dredges and the ground is craped up fairly often, the fishes appear in larger numbers.”


Fig. 3. Fishing in the mud. Tim Bunn (22/5/2008), Mud Fishing in India. Retrieved from youtube.com.


A Chain of Fishes

Aristotle imagined the spontaneous generation of such fish as a sort of chain. According to him, while very small fishes generate from foam that floats on the sea, larger fishes generate from the remains of the deceased smaller fish. A list is provided.

“From the aphya phalerica comes the membras, from the membras the trichis,[and] from the trichis the trichias.”

When the aphya phalerica dies, the membras generates from its decaying matter, when the membras dies the trichis generates from its remains, followed in due course by the trichias. As we can see, Gessner’s membras and aphya phalerica are mentioned here. This also explains why Gessner describes the former as springing from the latter. The aphya phalerica is the first stage in this chain of spontaneously generating fishes.


Fig. 4 A chain of fishes. Source: Clipartkid 


In the Footsteps of Aristotle

In Gessner’s day, Aristotle, as the founding father of natural history, was considered a much esteemed source of information. For this reason, Gessner and his contemporaries heavily relied on the information provided by him. Is this then a full explanation why Gessner believes these two fishes to generate spontaneously? It seems that Gessner was familiar with current catch records and market prices of the sprat, suggesting he had an informant who may have observed these species first hand. Surely someone like this, well-informed and possibly in possession of first-hand information, would know that the sprat springs from sexual generation as all other fishes do?

According to Aristotle this does not matter. He writes:

“the great majority of fish then, as has been stated, proceed from eggs. However, there are some fish that proceed from mud and sand, even of those kinds that proceed also from the pairing and the egg.”

Consequently, just because you have observed that a species sometimes comes from sexual generation, this does not mean they cannot also come from spontaneous generation. It really is quite hard to argue with that.


To Be Continued…

Is this all that is to be said on the aphya phalerica and the membras? Not quite. Closer inspection reveals that Gessner and Aristotle are not describing the same species. Where to Gessner an aphya phalerica is a sprat and a membras is a Baltic herring, to Aristotle the aphya phalerica was the anchovies and the membras something undefined, a large anchovies or another small fish. In a future blogpost we will explore this linguistic confusion.


Fig. 5 Sprats in tomato sauce. Source: Irina Slutsky 



Further reading:

Aristotle, History of Animals.

Conrad Gessner, Historia Piscium. Zürich, Froschauer, 1558.

Sophia Hendrikx, Identification of herring species in Conrad Gessner’s ichthyological works, a case study on taxonomy, nomenclature, and animal depiction in the sixteenth century. In: Paul J. Smith and Karl A.E. Enenkel (Eds.), Zoology in Early Modern Culture. Intersections of Science, Theology, Philology and Political and Religious Education. Leiden, Brill, 2014.


This post also appeared on the Leiden Arts in Society Blog.


© Sophia Hendrikx and Fishtories, 2017. Unauthorised use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Sophia Hendrikx and Fishtories with appropriate and specific direction to the original content.

Spontaneously generating, extremely oily fish

“These herring-like fish develop from other fish, which we have previously described as Schmelzling. They stay in the same place and were used by the Ancients to catch wasps and other pests.[1]

Thus a fish called membras is described in Conrad Gessner’s 1563 Fischbuch. As will be clear from the above statement, Gessner’s description of this species, in relation to the above mentioned Schmelzling which is described on the previous page, presents us with a few puzzling questions with potentially intriguing answers. In particular, this shows us how various sources of information could contribute to a sixteenth century naturalist’s research.



The membras


In order to work out the relationship between the membras and the Schmelzling, we should first of all consider the possibility that the former is a juvenile form of the latter. It was not unusual around this time to call a fish by different names at different stages in its life-cycle[2]. However Gessner consistently applies the same terminology when describing juvenile states of various species, and his description of the Schmelzling lacks this terminology. In addition, the accompanying illustrations, particularly the shape of the snout and the position of the fins[3], strongly suggest that even though these species are similar, they cannot be the same.

What, then, is the relationship between these two species?


The Schmelzling


The Schmelzling

Identification may bring us further information. The Schmelzling is described as a small species, with sharp scales on the keel. The latter characteristic suggests to a near certainty that we are dealing with a member of the herring family. In addition, the following is remarked on this fish:

 “This fish is so oily that it falls apart in your hands, and when they encounter fishing fleets a layer of oil forms on the water surface. Fishermen collect this oil and use it for their lamps[4]

All of this strongly suggests that the Schmelzling may be the sprat[5], which belongs to the herring family and is one of the oiliest fishes in existence. The illustration also appears to confirm this[6]. However this straightforward identification makes Gessner’s description of this species all the more puzzling.



Aristotle’s spontaneous generation

Gessner does not identify the Schmelzling as belonging to the herring family, but as a type of apua, specifically an apua phalerica. This term goes back to Aristotle who used it to describe various small fish which were said to generate spontaneously from the foam that forms on the surface of the sea near the coast[7]. Later these fishes develop into larger fish. Aristotle names the membras as one of these larger states, which develops from the apua phalerica.

As Gessner was thoroughly familiar with Aristotle’s work, it seems likely his description of the Schmelzling and membras is based on this. However elsewhere in his work, Gessner describes into detail and accurately how fishes procreate, and does not quote the spontaneous generation of fish as playing any part in this. Why is he doing so here? In order to solve the mystery of the Schmelzling and membras we should consider how Gessner dealt with his sources, and how he gathered information.


Aims and consequences

As a Renaissance naturalist Gessner operated in a tradition which sought to connect ancient nomenclature with the current by researching nature to identify the species described in the works of the ancients. However, in Gessner’s day the study of nature in this humanist tradition had spread from Italy to the rest of Europe. Based in Switzerland, as many fellow naturalists who were also based outside of the Mediterranean, Gessner encountered a range of species which had not been described by the classics. The description of such species, with the particular goal of explaining how these were different from those described by the ancients, became a crucial goal.

Such description demands a focus on the physical characteristics of different species as a means to tell them apart, which in turn brings a focus on observation and on depiction as a means of communicating information. Since observation of foreign species could be tricky due to both the financial cost of and the time needed for travel, whenever researchers were unable to study a species themselves they chose to rely on the testimony of others who had seen it. Crucial to this was the authority of the source, authors who were perceived as reliable were much more readily quoted. This explains Gessner’s decision to follow Aristotle.

However, since Aristotle did not provide illustrations, nor in fact described the sprat, Gessner must also have relied on another source of information to supply the depictions.


What is a membras?

Having identified the Schmelzling, let’s turn our attention to the membras. Taking into consideration that  observation tends to trump other sources in Gessner’s descriptions of species he had personally seen, we can safely assume that both the membras and the Schmelzling are species that could not be found in Switzerland. In addition, Gessner’s description of the membras states this is, like the sprat, a fish that belongs to the herring family[8]. This may help us, since Gessner provides a rough outline of the herring family in his description of the herring[9]. Here Gessner refers to two small ‘herring-like’ species that are common in the Baltic Sea; is it possible these are the two species discussed here? The sprat is extremely common in the Baltic Sea, as is a bigger ‘herring-like’ species, the Baltic herring.

The description of the physical characteristics of the Membras and the nomenclature seem to confirm this identification. In addition, the depiction of the Membras displays features that are typical of the Baltic herring, such as a long, angular snout, and pelvic fins that are positioned further back on the body than the origin of the dorsal fin.

If this identification is correct, we are indeed dealing with species which Gessner would have rarely seen himself. In addition, this identification could explain why Gessner found Aristotle’s theory of species developing out of smaller species appropriate here. The sprat and the Baltic herring are very similar-looking fish, and since the sprat is much smaller, someone who did not pay attention to the position of the fins might easily mistake it for a young Baltic herring.

Baltic herring

Baltic herring?


A Scandinavian informant?

However this still does not tell us how Gessner obtained the illustrations. The description of the Schmelzling may hold some clues. This states that on a good day a fisherman can catch 50 Kroner worth of it[10]. It seems therefore that Gessner was familiar with both current catch records and market prices for this fish.

As Gessner corresponded widely with acquaintances across Europe, he may have obtained this information from a correspondent who was more familiar with these species. Possibly this person provided him with nomenclature which seemed to correspond with Aristotle’s description, and very likely he remarked on the close similarity between the species. As these are Baltic sea fishes, it seems likely this person was based in Scandinavia. The reference to the currency Kronen is consistent with this assumption.

This trail ends here, but a search through sixteenth century books on fish reveals that both depictions previously appeared in Guillaume Rondelet’s 1554 Libri de piscibus marinis[11] and were made especially for this publication. Much like Aristotle, Rondelet was one of Gessner’s most esteemed sources of information. So much so in fact, that Gessner devoted a part of the introduction to the volume on aquatic animals of his Historiae Animalium to praising Rondelet’s systematic method in describing fishes.

In this case it turns out that Gessner’s description of both the membras and the Schmelzling are almost word for word based on Rondelet’s, who in turn follows Aristotle, but adds remarks on the physical characteristics of both species. The term Schmelzling cannot be found in the description by Rondelet, but the Latin nomenclature Gessner supplies, apua phalerica, is. Two further new elements were added by Gessner, the references to the current market value and the oiliness of the sprat, which must have come from Gessner’s mysterious Scandinavian source.


The old and the new

What we see here then, is a mix of contemporary information mixed with an ancient scholarly description. The information provided by Gessner’s Scandinavian source is effortlessly matched with Aristotle’s description and Rondelet’s rendition of this, providing us with a glimpse into how sources were often combined in order to cobble together a description of a species an author had not seen himself.

Notwithstanding the authority of Aristotle’s text, the contemporary sources were crucial to this. Not only did Aristotle did not provide illustrations, but his work also shows no great focus on the physical characteristics of species, both of which were vital ingredients to Gessner’s descriptions, since his focus lied on communicating the differences between species. This need was for the larger part met by the textual information and depictions provided by Rondelet, who shared Gessner’s approach to description and depiction. For interesting details such as the value and the extreme oiliness of the sprat, Gessner turned to his Scandinavian source.

Gessner’s focus on the physical characteristics of species and Aristotle’s theory of spontaneous generation reinforce rather than undermine one another, the differences between the sprat and the Baltic herring warranting careful description, and their similarity supporting the theory that one of these developed from the other.


This blogpost is based on a part of my article: Sophia Hendrikx, Identification of herring species in Conrad Gessner’s ichthyological works, a case study on taxonomy, nomenclature, and animal depiction in the sixteenth century. In: Paul J. Smith and Karl A.E. Enenkel (Eds.), Zoology in Early Modern Culture. Intersections of Science, Theology, Philology and Political and Religious Education. Leiden, Brill, 2014.


[1] “Ein kleine haring Art. Diese sollen von denen erwachsen, so wir zuvor schmelzling genennt haben, diese wpflegen allezeit an einem ort zubleiben, werden von etlichen alten gebraucht Wespen und ander dergleichen schädliche Thier zufahen.”

[2] In Gessner’s work (see Liber IV of his 1558 Historiae Animalium, his 1560 Nomenclator aquatilium animantium, and his 1562 Fischbuch) much attention is paid to different stages in the life-cycle of fish. Occasionally Gessner provides separate descriptions for the juvenile form of species which use a different nomenclature. Juvenile salmon for example, is described separately under the name Selmling.

[3] In particular the position of the pelvic fin in relation to the dorsal fin.

[4] “Dieses ist auch ein sehr kleiner Fisch, under am Bauch rauch, nach der haring Art, ist lind und so feißt, daß er einem under den händen zerschmilßt, so er hart angegriffen wirt. Dergleichen so veil zumal in einem Schifflin geführt werden, so geben sie Feißt von ihnen, so uber sich schwimt, von den Fischern auffgesamlet wirdt, unnd zu den Liechtern gebraucht.”

[5] Sprattus sprattus.

[6] In particular the position of the pelvic fin, which is implanted further forward on the body than the dorsal fin.

[7] Aristotle, History of Animals, vol. VI, part 15, trans. D’Arcy Wentworth Thompson (Oxford: Clarendon Press: 1910)

[8] Conrad Gessner, Fischbuch, 1563, f. 2 verso: “Membras. Ein kleine häring Art.”

[9] See: Sophia Hendrikx, Identification of herring species in Conrad Gessner’s ichthyological works, a case study on taxonomy, nomenclature, and animal depiction in the sixteenth century. In: Paul J. Smith and Karl A.E. Enenkel (Eds.), Zoology in Early Modern Culture. Intersections of Science, Theology, Philology and Political and Religious Education. Leiden, Brill, 2014.

[10] “Solche werden zur zeit deß Herbst in grosser menge gefangen, sind doch von etlichen Fischern auss einem Tag für 50. Kronen wehrt gefangen worden.”

[11] Guillaume Rondelet, Libri de piscibus marinis, 1554, part 1, p. 112 and 220.


Also see:

Conrad Gessner, Historiae Animalium – Rare Fish Books


Sophia Hendrikx and Fishtories, 2016. Unauthorised use and/or duplication of this material without express and written permission from this site’s author and owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to the author and Fishtories with appropriate and specific direction to the original content.