236 Proceedings of Philosophical Societies. (Serr. 
but they describe it only imperfectly ; and the moderns have formed 
different opinions respecting the plant to which the name should be 
applied. Some have supposed it to be the medicago arborea. M. 
de Berneaux, who has made an elaborate examination of the sub- 
ject, thinks that it is the cyéisus laburnum. But as Pliny speaks 
clearly of this tree under the name of laburnum, and as he ,con- 
siders it as different from the cytisus; and as some parts of the de- 
scription which Dioscorides gives of the cytisus does not agree with 
it entirely; it would seem that M. de Berneaux’ opinion on this 
subject is still attended with difficulties. What is always of great 
importance in such discussions, neither Pliny nor the other ancient 
naturalists were so accurate that they may not sometimes speak of 
the same plant under different names, or of different plants under 
the same name. } 
M. Dutrochet, a physician at Chateau-Renaud, interesting obser- 
vations by whom on the egg of the viper we mentioned in 1812, 
has generalized his researches, and has presented the results to the 
Class in a memoir on the envelopes of the foetus. We shall here 
communicate some of the propositions, remarking that they have 
not yet been constated by the Institute, because circumstances did 
not permit them to investigate the subject in the season which would 
have been suitable for the purpose; yet an extract of this memoir 
must be gratifying to physiologists, and may occasion new observa- 
tions on a subject obscure, though interesting. 
The author says that he has observed that at first the foetus en- 
closed in the egg has an opening at its abdominal walls and its 
amnios, through which passes an extension of the bladder, which 
forms the chorion and the middle membrane ; so that the umbilical 
vessels are only a production of those of the bladder. According to 
him, the egg of reptiles is a vitellus deprived of albumen, and in 
the viper the membrane of the cock of an extreme thinness disap- 
pears about the middle of the gestation, and then the naked chorion 
contracts adhesions with the oviducts without forming a true pla- 
centa. Thus this membrane of the cock would be analogous to the 
membrana caduca of mammiferous animals. He affirms that the 
tadpole does not throw off its skin in order to undergo a metamor- 
phosis, but that the anterior feet pierce that skin, that the jaws tear 
it, and the openings cicatrize. The egg of the frog, and of this 
class of animals in general, is a vitellus, the emulsive matter of 
which is contained in the intestine itself, which, at first globular, is 
elongated by degrees in a spiral tube, such as we see it in the tad- 
pole. M. Dutrochet has likewise very particular ideas about the 
respiration of the foetus, and particularly about the bronchie of 
tadpoles, which he considers as placed in the cavity of the tym- 
panum. We shall speak of them at greater length when it shall be _ 
in our power to verify them, and to throw some light on their 
nature. 
Comparative anatomy had not determined the nature of the re- 
spiratory organs of the cloporte. It was known that these’animals 
6 
