ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 
393 
enters through the wall of the thread and of the capsule, hut there is 
some other cause of the actual shooting out of the thread. The author 
adheres to his theory that the sub-epithelial nerve-plexus inhibits the 
expulsion, which he regards as reflex. He concludes less optimistically 
than he did in his summary of ten years ago, when he spoke of our 
knowledge of the functioning of the stinging cells as satisfactorily 
complete. 
Aliciidae.* — Mr. J. E. Duerden recalls his study of Alicia costse Pane, 
and Cystiactis tuberculosa Quoy and Gaim., which showed the necessity 
of separating them from the Bunodidae, and the erection of a new family 
Aliciidae. He has since been fortunate in obtaining an authentic speci- 
men of A. mirabilis (the type of the genus) from Mr. J. Y. Johnson, 
who founded the genus in 1861. He also describes a new species of 
Bunodeojpsis, B. antilliensis, and compares it with the type B. strumosa. 
To Alicia, Cystiactis , and Bunodeojpsis, the genus Thaumactis Fowler has 
also to be added. The family diagnosis is as follows : — Hexactinece, 
with a large flat contractile base. Tentacles simple, subulate, and 
entacmaeous. Column with simple or compound hollow outgrowths or 
vesicles over more or less of its surface, arranged mostly in vertical 
rows. No cinclides. Sphincter muscles endodermal and diffuse, variable 
in amount of development. Perfect mesenteries few or numerous. No 
acontia. 
Porifera. 
Position of Sponges in the Animal Kingdom.f — Mr. E. A. Minchin 
has a learned article on this difficult problem. He states the case for 
Sponges, as (1) Protozoa, (2) Metazoa, and (3) neither. The majority 
are in favour of sponges being Metazoa ; but then the alternatives crop 
up — are they Coelentera, or do they represent a distinct phylum ? 
The four points of primary importance in the discussion of the 
affinities of Sponges are : — (a) The unfailing possession of collar-cells, 
and their great resemblance to Choanoflagellata ; ( b ) the reproduction 
by ova and spermatozoa ; (c) the formation of two germ-layers by pro- 
cesses not specially characteristic of sponges, and the possession of a 
larva very similar to the coelenterate planula ; and (d) the reversion 
of the germ-layers at metamorphosis — a fact which is quite subversive 
of the coelenterate theory. 
We have but two theories, the author says, to choose between : — either 
to regard sponges, with Biitschli, Sollas, and Delage, as descended from 
choanoflagellate ancestors independently of the Metazoa ; or to regard 
them, with Maas and, apparently, Balfour, as true Metazoa, whose two 
primary germ-layers have become reversed in position in the adults. 
The author inclines to the second alternative, but says we should be 
cautious in pinning our faith to either. Perhaps there is yet another. 
Hexactinellids with Discoctasters.J — Prof. J. Ijima gives a general 
description of the structure of the Hexactinellida which have those 
strongly modified discohexasters which F. E. Schulze called discoct- 
asters. This peculiar kind of spicule has hitherto been known to occur 
* Arm. Nat. Hist., xx. (1897) pp. 1-15 (1 pi.). 
f Science Progress, i. (1897) pp. 426-60. 
X Annot. Zool. Japon., i. (1897) pp. 43-59. 
