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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.


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