Metamorphosis of the Common Eel. 269 



vulyaris, because from them Dr. Raffaele obtained prse-larvse which 

 had only forty-four abdominal myomeres. T endeavoured for two 

 years in vain to study these eggs at the Zoological Station of Naples. 

 I found only a few of them, and these died prematurely. 



In another point my researches have yielded a very interesting 

 result. As a result of the observations of Petersen, we know now 

 that the Common Eel develops a bridal coloration or " mating 

 habit," which is chiefly characterised by the silver pigment without 

 trace of yellow, and by the more or less black colour of the pectoral 

 tin, and finally by the large eyes. Petersen inferred that this was 

 the bridal coloration from the circumstance that the individuals 

 exhibiting it had the genital organs largely developed, had ceased to 

 take nourishment, and were migrating to the sea. Here Petersen's 

 observations cease and mine begin. The same currents at Messina 

 which bring us the Leptocephali bring us also many specimens of 

 the Common Eel, all of which exhibit the silver coloration. Not a 

 tew of them present the characters described by Petersen in an 

 exaggerated condition, that is to say, the eyes are larger and nearly 

 round instead of elliptical, whilst the pectoral fins are of an intense 

 black. It is worth noting that in a certain number of them the 

 anterior margin of the gill slit is intensely black, a character which I 

 have never observed in eels which had not yet migrated to the sea, 

 and which is wanting in the figures and in the originals sent to me by 

 Petersen himself. Undoubtedly the most important of these changes 

 is that of the increase of the diameter of the eye, because it finds its 

 physiological explanation in the circumstance that the eel matures in 

 the depths of the sea. That, as a matter of fact, eels dredged from 

 the bottom of the sea have larger eyes than one ever finds in fresh- 

 water eels, I have proved by many comparative measurements, made 

 between eels dredged from the sea bottom and others which had not 

 yet passed into the deep waters of the sea. Thus, for instance, in a 

 male eel taken from the Messina currents and having a total length 

 of 34 J cm., the eye had a diameter, both vertical and transversal, of 

 9 mm., and in another eel of 33 J cm., the same measurement was 

 recorded. In a female eel, derived from the same source and 

 purchased in the market, whose length was 48 \ cm., the vertical 

 diameter of the eye was 10 mm., and the transversal diameter rather 

 more than 10 mm. These are not the greatest dimensions which I 

 observed, and I conclude from these facts that the bridal habit 

 described by Petersen was not quite completed in his specimens, and 

 that it becomes so only in the sea and at a great depth. In relation 

 'to these observations of mine stands the fact that the genital organs 

 in the eel taken in the Messina currents are sometimes more 

 developed than in eels which have not yet entered the deep water. 

 Thus it has happened that male individuals have occurred showing 



