TUNICATA, POLYZOA. 
211 
derm towards the underside. The dorsal disk in the solitary form makes 
its appearance between the ectoderm and mesoderm, nervous centre and 
intestine, just as the chorda dorsalis in the Yertebrates, and there are 
also organs which the author thinks analogous to the amnion and pla- 
centa ; even in the young aggregate individuals, although they want a 
placenta, there is something like umbilical circulation. Thus there are 
some points in which the development of the Salpce resembles that of 
even the higher Vertebrates. The mantle is considered by the author to 
be of epidermic nature [as also by Semper]. Atti Acc. Rom. (2) ii. 
pp. 720-792, pis. ii.-v. An abstract of the author’s previous communica- 
tion is to be found in Q. J. Micr. Sci. (2) xv. p. 87. 
POLYZOA. 
J. Barrois states that the larval forms of different genera of Bryozoa 
are identical in the A Icyonidiidce and Vesiculariidm from the first to the 
bell-shaped stage, though afterwards the histological differentiation and 
completion of the organs is very different in different genera and fami- 
lies. 0. R. Ixxxi. pp. 442 ; abstract Ann. N. H. (4) xvi. pp. 301 & 302. 
W. Repiachoff observes that in Tendra zostericola (Nordm.) some 
zooecia contain only an ovarium, others only male elements, and others 
both together ; he describes the first appearance of the egg, and the 
swimming larva, in which a dorsal and ventral face, and on the latter a 
tuft of cilia, a sort of oesophagus, and a protractile sucker, are to be seen 
The internal and external changes which the larva undergoes after fix- 
ing itself are mentioned and compared with those observed by Nitsche 
and Clapar^de in Bugula ; the chief difference is, that the brown body 
or formative mass is contained inside the intestine, and that therefore 
the development of the middle and posterior part of the intestine is in 
the primary zooecia different from that of the secondary zooecia. The 
tentacular sheath consists of two distinct layers, both in young and 
full grown polypids, the inner layer being continuous with the epithelium 
of the tentacles, the inner layer of which gives origin to their muscular 
layer. Z. wiss. Zool. xxv. pp. 129-142, pis. vii.-ix. 
H. Nitsche describes the budding of Alcyonella fungosa (Pall.), espe- 
cially as to which layer of the cystid is continuous with and gives origin 
to the individual organs of the polypid ; viz. : — the ectocyst to the out- 
side of the tentacles, the epithelial layer of the intestinal tract of the 
polypid, and the ganglion, and the endocyst to the inner layer of the 
tentacles, the outer layer of the intestinal tract, the wall of the peri- 
toneal cavity, and the cover of the ganglion ; all these organs are formed 
by inward folded processes of the cystid, some of which meet and 
coalesce. This appears to be the case in all Bryozoa Phylactolcema. If 
the polypid and cystid are to be regarded as distinct individuals, accord- 
ing to Ailman, Leuckart, and Nitsche himself, it follows that the ecto- 
derm of the parent gives origin to the endoderm of the descendant, and 
vice versa. In Loxosoma^ on the contrary, and probably in all Bryozoa 
Endojprocta, the ectoderm of the parent alone gives origin to the whole 
bud, in which afterwards ectoderm, mesoderm and endoderm can be dis- 
