ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
457 
anterior invaginable part of the skin all have their long axes set trans- 
versely^to the long axis of the body, so as to afford the least resistance 
on contraction. The skin of this part of the body is much thinner and 
weaker than the rest. 
The whole of the water-vascular system is surrounded by an elastic 
membrane, as is probably the case in all Echinoderms ; the degree of 
development of the membrane in the podia depends on the needs of the 
animal. The stone-canal is fused with the efferent duct of the gonads. 
Spermatogenesis is so far different from that of all other known Echino- 
derms that long spermatogemmae are formed. The brood-pouches are 
invaginations of the skin which are always open to the exterior ; from the 
way in which the ova pass into them it may be supposed that the eggs are 
deposited on the sea-bottom, and that the animal creeps over them, and 
takes them into the pouches ; at this time there are probably peristaltic 
movements of the circular musculature of the efferent ducts of the 
pouches. There is no direct connection between gonads and brood- 
pouches. The generative products are formed at different periods, 
separated from one another by intervals of unknown length, during 
which no generative products are formed. 
Cleavage of eggs 1 mm. in diameter is not, as in other Echinoderms, 
total ; the cleavage-nuclei are scattered in the midst of the large unseg- 
mented yolk, and migrate, as they increase in size, to the periphery, 
where they form the ectoderm. The yolk breaks up into large spheres. 
When the young are almost complete they have the mouth closed by a 
plate of cells, so that no nutriment can be ingested at this stage. The 
brood-pouches probably serve only for the protection of the young. The 
gonads arise in the mesentery in the form of a small mass of cells, which 
at first gives off a pair of genital tubes, and later on the duct. Later on 
other genital tubes arise by pairs from those already formed. 
Development of a Holothurian Spicule.* — Mr. K. Kishinouye de- 
scribes and figures the various stages in the growth of the spicules of a 
Japanese Holothurian, an abstract of which would be hardly intelligible 
without the ten illustrative figures, 
Coelentera. 
Asexual Reproduction of Madrepora.f — Dr. G. v. Koch has studied 
the gemmation of the skeleton in M. ecJiidnsea and M. surculosa. The 
buds arise from processes of the costae of the mother calycle, which first 
form blunt triangular projections above the edge of the costa, and then 
form thin bridges of connection, which are the first signs of a wall. 
The later swallow-nest-like form of flie bud is due to the more rap>id 
growth of the two outer costal processes ; of the septa the two primaries 
are direct continuations of one costa of the mother-polyp, while the 
others are partly direct continuations of the costae and partly new 
formations. In older buds the costae increase by fission. 
Flabellum anthophyllum.t — Prof. II. de Lacaze-Duthiers points out 
that this coral, which he has studied on the shores of the Gulf of Lyons, 
* Zool. Anzeig., xvii. (1894) pp. 146 and 7. 
f Abh. Nuraberger Nat. Gesellsch., 1893, 18 pp., 1 pi. and 3 figs. See Zool. 
Centralbl., pp. 101 and 2 (2 figs.). % Comptes Rendus, cxviii. (1894) pp. 1013-9. 
