ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
467 
system is bilaterally symmetrical, although the symmetry is hidden by 
the changes which take place in the position of the plane of symmetry 
during growth. The author cannot accept the account given by Seeliger, 
who met with difficulties in Salpa democratica that are not to be found 
in S. pinnala, where the stolon is straight. 
The cavity of the pharynx arises by the degeneration of the visceral 
follicle cells ; its endodermal epithelium is derived from the blastomeres, 
and the gut is formed as a diverticulum of the pharynx. 
In the concluding paragraphs the author describes the endodermal 
tube of the stolon, and the digestive tract of the aggregated Saljpa ; here 
again he compares his results with the results of Seeliger and Salensky. 
Nutrition of Embryo of Salpa.* — Prof. W. K. Brooks points out 
that the generally accepted idea that the nourishment and aeration of 
the embryo of Salpa is on the same lines as that of the Mammalian 
foetus is quite incorrect. As the Salpa-e mbryo is bathed by the water 
which is constantly flowing past it, there does not seem to be either any 
need for or adaptation of structure for a respiratory placenta. Nourish- 
ment, moreover, is effected in a way quite unlike anything which has been 
described in the Mammalia. 
The remarkable and rapid growth of the young Salpa is only partly 
due to cell-multiplication, for there is a growth of the individual cells, 
which, instead of growing smaller with repeated divisions, actually 
increase in size in all parts of the body. The placenta of Salpa is an 
organ for the nourishment of the cells of the placenta by the blood of the 
chain -Salpa ; and the subsequent degeneration of these cells, after they 
have migrated into the body of the embryo, supplies the material for the 
growth of the embryo. It would seem that those investigators who 
have described the placenta as divided into a foetal chamber and a 
maternal one have been misled by an erroneous notion as to its function. 
The placenta is not the only nutritive organ, as the follicle also 
supplies material which is available for the rapid construction of the 
body of the embryo. The cells of this follicle become detached and 
degenerate, and though it is not possible to trace the history of every 
cell from first to last there is sufficient evidence that the function of the 
follicle of Salpa is exclusively nutritive; the organ is transitory and 
embryonic. 
New Species of Octacnemus.j — Mr. M. M. Metcalf describes a 
deep-sea Tunicate from Patagonia, which shows many resemblances to 
0. bithyus of Moseley, but differs from it in being colonial and not 
solitary. It may, of course, be the chain-form and Moseley’s the solitary 
form of one and the same species. Meantime it is called 0. patagoni- 
ensis. 
£. Bryozoa. 
Classification of Cheilostoma.j: — In an essay on British Palaeogene 
Bryozoa, Mr. J. W. Gregory proposes the following classification of the 
order Cheilostoma: — 
* 
t 
John Hopkins Uuiv. Circ., xii. (1893) pp. 97 and 8. 
Tom. cit., pp. 98-100 (6 figs.). 
