Miscellaneous. 111 
the same individuals for more than two months, and to see the organs 
form and the young Molgula become complete 
In this abstract it would be difficult to give any details with re- 
gard to the transformations of the tissues and the formation of the 
regarded by all zoologists as one of the most certainly established. 
A ‘fact so unexpected must show what reserve and n e should 
always guide us in zoological generalizations. F ther’ was 
no induction more legitimate than that which ciel fa all the Asci- 
dians a tadpole-like embryo; and yet the Molgule do not fall under 
this general rule. 
In this remarkable exception we also certainly find a fresh example 
geny may and must furnish pu information, by itself it may also, 
in some cases, lead us into the gravest errors. Of this, Molgula, 
by the Petr iae orm B its PE S a proof,— Comptes 
Rendus, May 30, 1870, tome Ixx. p. 
On the Embryonal ue mdi d: mu proboscideus. 
By E 
Kölliker has already eee that in B pee proboscideus 
oly part of the contents of the ovum is employed in the formation 
f the embryo, and that the remainder forms a layer of peripheral 
sail, the fate of which was unknown to him. M. Knoch has re- 
cently questioned the accuracy of this observation, ns it appears, 
erroneously. Mecznikow describes the ova of t estoid worm as 
occupied by an ovarian cell surrounded by a mass of antes vitellus, 
The cell pues ms complete segmentation, whilst the vitelline mass 
re no part in the formation of the embryo. From the cellular 
ass pro er by segmentation, two cells, furnished with larger 
sakes than the rest, soon ge ; they fix themselves at the two 
poles of the ovum, and do not disappear un e close of em- 
bryonic life. The author e seen a perfectly similar arrangement 
in the ova of Tenia cucumerin 
After segmentation the mass sof embryonal cells acquires a rounded 
form; and the embryo divides into a central nucleus and a peripheral 
mass formed of very evident cells. the nucleus forms the 
pheral cells becomes connected into a delicate membrane, which 
finally loses its cellular structure, and acquires the appearance of a 
homogeneous cuticular envelope. 
though this envelope of the embryo never becomes covered with 
vibratile cilia, Mecznikow does not hesitate to compare it to the 
ciliated envelope of the larva of Dicikeiscephalis latus. This « com- 
