184 
MOLLUSCOIDA. 
dorsal and ventral side of these animals^ in the saihe manner as 
the late Keferstein. 
A short abstract of Kowalewsky’s and Kupifer’s researches concerning the 
embryology of Ascidias is to be found in Journ. Micr. Sc. 1870^ pp. 69-69 
and 299. 
Dr. W. Donitz opposes these views. He states, from obser- 
vations on Clavellina lepadiformis (Miill.), made by him at 
Naples, that the cleaving of the yelk and the formation of 
a yelk-membrane is here as usual, that the intestine is not 
formed by any invagination, that the central nervous system, as 
described by Kowalewsky, is not found in the larvae of Clavellina , 
and concludes that the string of cells, intermixed with vacuoles, 
in the axis of the tail of those larvae is only apparently similar 
to the chorda of a vertebrate, but really quite different, — these 
cells being arranged concentrically, and not in bilateral order, 
and nothing like a vertebra being associated with them j he 
thinks it even very doubtful if the adjoining cells can be regarded 
as muscular cells. SB. nat. Fr. 1870, pp. 47-51 ; also in Arch. 
Anat. u. Phys. pp. 161-164. 
M. Gan IN, from his observations on the development of the 
compound Ascidise (see below) , comes to the conclusion that the 
nervous system of the embryo is, in its development, in its form, 
in its structure, and in its local relations to the other organs, 
more similar to the nervous system of the embryo of the Verte- 
brata than to that of any other embryo or full-grown animal. 
The ciliated pit in the Ascidise is to be compared to the nasal 
organ of Amphioxus, He coincides, therefore, with KowalcAvsky 
[and Kupffer] as to the affinity of the Ascidise in their embryonic 
stage with the Vertcbrata, and refutes the objections made by 
Meeznikow (Zool. lice. vi. p. 591). Z. wiss. Zool. xx. pp. 513, 
517. 
Lacaze-Duthiers, studying the development of various genera 
of Ascidians by means of artificial fecundation, observed tlie very 
strange fact that the embryo of what he believes to be Molyula 
tubiifosa is widely different from that of others, being an un- 
formed mass, with slow amoeboid motion. C. R. June 1870, 
and 11. Z. 1870, pp. 206-209 ; translated Ann. N. H. (4) vi. 
pp. 109-111. 
A. Hancock points out that a tadpole-like larva, like that of 
other Ascidise, has also been observed by Van Beneden in a real 
Molgula, ampulloidea (Beneden), and by himself inM. complanata, 
sp. n. ; and he suggests that the animal observed by Lacaze- 
Duthiers was not a true Molgula, but Eugyra arenosa, Aid. and 
Hanc. His observation, however, is not tlie less interesting on 
that account. Ann. N. 11. (1) vi. pp. 353-355. 
Ascidia plana^ alderif i'ubrotincta, 7'ubicimda, I'obusta, mollis^ ct'assa, vnornata, 
