304 Miscellaneous. 
Lastly, we can prove the disappearance of one of the two embryonic 
membranes, the amnios. The disks which surround the digestive 
tube are not here composed of hollow sacs, but of solid lamelle ; so 
that a single membrane, the skin of the Nemertes, results from their 
union. In a word, we see manifested under our eyes a remarkable 
tendency to the suppression of the exaggeration of the larval state 
which constitutes the Pilidium, and to a return to the direct mode 
of development. 
Here, then, we have, by the side of a development very like that of 
the Pilidium, a very great simplification and an evident condensation 
of the embryogeny. One step further and we arrive at the extreme 
condensation which is observed in the larvee of Desor. We have 
therefore before us an intermediate stage between the Pilidium and 
the larva of Desor; and this result seems to be of incontestable 
importance. It enables us to correlate the two widely different 
forms of the embryos of the Nemertians, and shows us that the 
mutual relations which exist between them are analogous to those 
which Fritz Muller has informed us exist between the Nauplius and 
the Zoéa. Like the Nauplius, the Pilidium is the primitive form ; 
and the larva of Desor represents a condensed form derived from the 
former by the abbreviation of the embryogeny.—Comptes Rendus, 
January 25, 1875, pp. 270-273. 
On the Reproductive Organs of the Eels. By M. Syrsx1. 
In 1872 two memoirs appeared almost simultaneously by Italian 
authors, who announced that they had discovered that the eels are 
hermaphrodites. The agreement in general results was certainly 
adapted to inspire some confidence; but, on the other hand, con- 
siderable divergences in the descriptions of the organs showed that 
the question was far from being completely cleared up. These 
differences might arise from errors of observation ; or they might be 
ascribed to differences of organization due to the species, age, or sex 
of the fishes examined. 
According to M. Syrski all that relates to the male organs in these 
two memoirs is completely erroncous, and the eels are not herma- 
phrodites at all; MM. Balsamo-Crivelli and Maggi were the sub- 
jects of an illusion when they thought they had ascertained the 
presence of spermatozoids; the organs regarded by them as the 
testes are nothing more than fatty bodies. 
Notwithstanding the assertions of the preceding authors, and the 
gap which exists in the researches of M. Syrski, the probabilities 
seem to be entirely in favour of the unisexuality of the eels. 
In these fishes the males are smaller than the females. Eighty- 
six individuals, 218-430 millims. in length, examined by M. Syrski 
proved to be males; and ninety others, 275-1050 millims. long, 
were females. The previous observers having preferred examining 
large individuals, had only females under their inspection. 
The testes appear as nearly symmetrical paired organs, in the 
form of long ribbons, attached, like the ovaries, along the dorsal 
wall of the abdominal cavity, That of the right side commences a 
