518 ZOOPHYTA. CORALLINAD^. Alcyomdm. 



aggregate fleshy tubular cells of polypi, having about 12 radiating short ten- 

 tacula. It is the drying of the tubes that forms the rigid spinulse." 



89. A. parasiticum. — I place here provisionally a parasitical 

 species, which invests the old stalks of several of the Sertula- 

 riadcB. It is destitute of fibres, but strengthened by denser 

 bands, which, by anastomosing irregularly, enclose the spaces 

 of the cells ; these seem to have rounded orifices, and to be dis- 

 tant from each other ; the surface is rugose when old, the ori- 

 fices of the cells becoiTie more apparent, and the whole much 

 mixed with mud. I have not had an opportunity of observing 

 it in a recent state. 



Gen. XLI. CRISTATELLA.— Body gelatinous, branch- 

 ed, with terminal polypiferous papillae ; the circle of tenta- 

 cula disposed in the form of a crescent. 



90. C. campanulata. — Body divided, palmate. 



Polype a panache d'eau douce, Trembly^ Pol. p. 227- t. x. f. 8, 9 — Tubu- 

 laria camp. Linn. Syst. 1303. Berk. Syn. i. 215. Turt. Brit. Fauna, 

 211. — Adheres to Lemnse. 

 The body is translucent and palmately branched, the ends of the branches 

 forming cells ; the body of the polypi is cylindrical, where exserted, narrow at 

 the summit, with numerous tentatacula ; an esophagus, stomach and intestine, 

 together with two threads, descending into the fleshy base, are observable. 

 It may admit of doubt whether the animal described by Roesel (iii. 559. 

 t. xci.) constituting the Cristatella mucedo of Cuvier, and Cristatella vagans of 

 Lamarck, and which is free, belongs to the same genus with the Polype a pa- 

 nache of Trembly, above referred to, which seem to be fixed., and to be near- 

 ly related to the genus Plumatella. 



SPONGIAD^. 



The sponges, which have long occupied the attention of naturalists, 

 and given rise to considerable difference of opinion regarding their 

 true place in the System of Nature, have at length been examined 

 by an observer possessing the requisite leisure, opportunity, industry, 

 and talent for conducting such intricate researches. I here refer to 

 the papers which have appeared in the Edinburgh Philosophical Jour- 

 nal by Dr R. E. Grant, now Professor of Zoology in the University of 

 London. He has succeeded in determining the functions of the pores, 

 and the origin and mode of development of the ova. 



Sponges consist of an albuminous skeleton and gelatinous matter, 

 forming a mass not irritable, with numerous holes, connected internal- 

 ly with anastomosing canals. The skeleton is either simple, consisting 



