ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 899 



ment is driven througli the canals by means of the ciliated cells, aided 

 by muscular contractions ; the vessels are so extensile as to be able 

 to take in iishes of some considerable size. The undigested parts — 

 the skeleton of Crustacea, for example — are returned by the orifice 

 through which they entered. We find, then, that the Ehizostomidge 

 differ so far from the other Medusse that digestion does not take place 

 in the stomach, but in the frills and canals. The function of the 

 accessory urticating and other organs is then discussed, and it is 

 found, as might be expected, that they give some aid in attacking the 

 prey. The author insists in his resume on the morphological fact 

 that every series of frills has its own vessel. 



Porifera. 



Supposed Heteromorphic Zooids of Sponge.* — Professor E. P. 

 Wright describes, as the representative of a new genus and species, 

 a sponge from one of the Seychelles Islands which he names Alemo 

 seychellensis. It is closely allied to the genus Teihea Schmidt, if, 

 indeed, the possession of three distinct forms of stellate spicules, and 

 of the apparently dimorphic bodies here called zooids, is sufficient to 

 separate it from that genus. The heteromorphic zooids referred to are 

 spiculose, pedicellate bodies, which are projected from the main mass 

 of the sponge, at right angles to it. Two forms of these bodies are 

 distinguished ; the one is ovoid, almost smooth, and terminated by an 

 osculum ; the other is irregularly fan-shaped. These two kinds occur 

 together in couples, and are interpreted as being two distinct forms of 

 zooids. These remarkable formations appear, however, as surmised 

 by the author, to be simply instances of that form of gemmation which 

 is a far from uncommon occurrence in the genus Teihea, and which 

 has been also observed in the kindred genus Binalda. The dimor- 

 phism of the buds is an interesting fact which stands in need of 

 further elucidation. 



Habits and Structure of Clione.f — N. Nassonow finds that 

 these boring sponges live on the shells of living oysters as well 

 as on empty shells. They give off from the surface very delicate 

 pseudopodia-like processes, which pass in all directions into the sub- 

 stance of the shell ; these processes may branch, and even anastomose 

 with one another. The author, by placing in the aquarium fine trans- 

 parent lamellae of oyster-shells, saw the young Clione push its pro- 

 cesses into the calcareous lamellss ; when they had reached a certain 

 depth they united with one another, and forced out hemispherical 

 calcareous particles ; these were by contraction carried into the 

 interior of the body, and then cast to the exterior. The ectoderm 

 is reported to consist of fiat, colourless epithelial cells, with processes, 

 by means of which the cells are connected together ; the mesoderm is 

 formed by a mass of layers of oval, yellow cells. 



Soft Parts of Euplectella aspergillum.:}:— In spite of its famili- 

 arity to naturalists and the world at large, no satisfactory account of 



* Trans. Roy. Irish Acad., xxviii., pp. 13-20 (1 pi.). 



t Zool. Anzeig., iv. (1881) pp. 459-60. 



I Trans. Roy. See. Edinburgh, xxix. (1880) pp. 661-73 (1 pi.). 



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