Page:Proceedings of the Royal Society of London Vol 60.djvu/294

268 •confounded w ith th e pigm ent round the posterior extrem ity of the brain, which latter is already present in the preceding stage. In specimens taken at the m ouths of rivers this more or less superficial pigment was, so far as I could ascertain, always present.

As the pigm entation develops itself, the little eel gradually undergoes a dim inution in all its dimensions. I t results from my m easurements, th at the fully pigm ented elver has an average length of (31 mm., while for the more or less colourless elver the average length is 67 mm. I found pigm ented elvers which were reduced in length to 51 mm., a size which I never observed in those elvers in which the development of pigm ent had not taken place.

The facts which I have stated dem onstrate th at the eel goes through a metamorphosis, and th at brevirostris is its larva. Some fu rth er considerations rem ain to be given, although I believe th at zoologists will not consider the question still an open •one after the record of facts given above—facts, which anyone may verify by examining the m aterial which is preserved in my hands. Many to whom I have related my discovery of the history of the Common Eel have objected th at eels are found almost everywhere, w hilst Leptocephalus brevirostris is lim ited to Messina. In reply, I m ust say th at, first of all, it is not true th at Leptocephalus brevirostris is lim ited to M essina; secondly, th a t at Messina there are special currents, which tear up the deep-sea bottom which everywhere else is inaccessible; thirdly, although it is true th at on the coasts of many countries where Anguilla vulgaris is found, no one has ever seen a Leptocephalus brevirostris ; it is also true th at in no country, not even in those where eels are abundant, has anyone ever seen an eel of less than 5 cm. in length. Since it has to be adm itted th at no one knows the eel before it arrives at the length of 5 cm., there is no greater difficulty in supposing that during this unknown period the eel passes through a Leptocephalus stage than in supposing th at it does not do so. The critical study of the literature of this subject, and a great many continued observations, have occupied me for many years, and have been undertaken just in those places where young eels are to be found. They enable me, from my own studies, to affirm with assurance th at young eels w ith the definitive adult form do not exist of less than 5 cm. in length.

From the study of the memoir of Raffaele on pelagic eggs, I have come to the conclusion that the eggs of his undetermined species No. 10, having a diameter of 2’7 mm. and differing from all the others in the absence of oil globules, must belong to the Anguilla