ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
461 
number aud arrangement of tlie tentacles ; the gonads vary also, though 
not so much. A description is given of what seems to be a new species 
of Saliclystus, but it is not named. 
Porifera. 
Embryology of Porifera.* * * § — Mr. E. A. Minchin gives a useful sum- 
mary of the present state of our information regarding the development 
of Sponges, a group as to which such diverse views are held, and such 
opposing explanations given. Specially are the works of Delage and 
Maas considered. 
On this subject Mr. H. Y. Wilson’s review f should also be con- 
sulted. 
Nutritive and Excretory Processes in Porifera.f — Mr. A. T. Mas- 
terman, from the study of Grantia cornpressa, finds that food-particles are 
chiefly ingested by the choanocytes, and that their absorption by other 
parts is practically of no importance. The choanocytes may become 
transformed into amoebiform cells, which in no way differ in appearance 
from the so-called mesoderm cells. These cells migrate inwards and 
exhibit intracellular digestion ; their place is taken by fresh choanocytes 
which arise from transformed “mesoderm cells.” The solid waste 
particles are excreted by amoeboid nephrocytes, which burst through the 
limiting layer of pinnacocytes, and leave the colony, probably to disin- 
tegrate. 
Although the author does not discuss the bearing of his facts on the 
much disputed point of the origin of the Porifera, it is clear that the 
fact that the cells of the inner layer are, under; different conditions, 
mastigopod or myxopod strengthens the argument in favour of the 
Choanoflagellate relationship, while the absence of intracellular digestion 
distinguishes Sponges from Coelentera. 
Comparative Anatomy of Sponges.§ — In the sixth of his “ Studies,” 
Dr. A. Dendy deals with the anatomy and relationships of Lelapict 
australis , a living representative of the fossil Pharetrones. This very 
remarkable calcareous Sponge is very rare, and has only been dredged 
off the coast of Victoria. As the author had suspected, the canal system 
belongs to the Leuconoid type, but what is most interesting is the as 
yet unobserved reticulated fibrous character of the skeleton ; unknown 
in any other living calcareous Sponge, this character forms the most 
prominent feature in the great fossil group Pharetrones. 
The spicular fibres are believed by the author to be derived from 
the articulate tubar skeleton of a Syconoid ancestor ; reasons are given 
for this view, and it is pointed out that, while in Leucandra the spicules 
of the primitive articulate skeleton become scattered and disjointed, 
they retain their mutual relationships in Lelapia, where the very peculiar 
shape of the spicules facilitates the formation of fibres. Lelapia may 
continue to be looked on as an offshoot from the great family Grantiidee, 
in proximity to Leucandra. 
* Science Progress, i. (1894) pp. 208-33. 
f Amer. Natural., xxviii. (1894) pp. 439-41. 
% Ann. and Mag. Nat. Hist., xiii. (1894) pp. 488-96. 
§ Quart. Journ. Micr. Sci., xxxvi. (1894) pp. 127-41 (1 pi.). 
