Page:Proceedings of the Royal Society of London Vol 60.djvu/295

Rh vulgaris, because from them D r. Raf'faele obtained proe-larvse which had only forty-four abdom inal myomeres. I endeavoured for two years in vain to study these eggs at the Zoological Station of N aples. I found only a few of them, and these died prematurely.

In another point m y researches have yielded a very interesting result. As a result of the observations of Petersen, we know now th at the Common Eel develops a bridal coloration or “ m ating habit,” which is chiefly characterised by the silver pigm ent w ithout trace of yellow, and by the more or less black colour of the pectoral fin, and finally by the large eyes. Petersen inferred th at this was the bridal coloration from the circum stance th a t the individuals exhibiting it had the genital organs largely developed, had ceased to take nourishm ent, and were m igrating to the sea. H ere Petersen’s observations cease and m ine begin. The same currents at Messina which bring us the Leptocephali brin g us also m any specimens of the Common Eel, all of which exhibit the silver coloi-ation. N ot a few of them present the characters described by Petersen in an exaggerated condition, th at is to say, the eyes are larger and nearly round instead of elliptical, w hilst the pectoral fins are of an intense black. It is w orth noting th at in a certain num ber of them the anterior m argin of th e gill slit is intensely black, a character which I have never observed in eels which had not yet m igrated to the sea, and which is w anting in the figures and in the originals sent to me by Petersen himself. Undoubtedly the m ost im portant of these changes is th at of the increase of the diam eter of the eye, because it finds its physiological explanation in the circum stance th at the eel m atures in the depths of the sea. That, as a m atter of fact, eels dredged from the bottom of the sea have larger eyes than one ever finds in freshwater eels, I have proved by m any com parative measurem ents, made between eels dredged from the sea bottom and others w hich had not yet passed into the deep w aters of the sea. Thus, for instance, in a male eel taken from the Messina currents and having a total length of 34^ cm., the eye had a diam eter, both vertical and transversal, of 9 mm., and in another eel of 33^ cm., the same m easurem ent was iecorded. In a female eel, derived from the same source and purchased in the m arket, whose length was 48|- cm., the vertical diameter of Ihe eye was 10 mm., and the transversal diam eter rather moie than 10 mm. These are not the greatest dimensions which I observed, and I conclude from these facts th at 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 th at 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, lh u s it has happened th at male individuals have occurred showing