151 



Opcrciiliva, and in others quantities of diatoms and algal 

 growths. Where such are present the stomodoeal epithelium 

 and the mesenterial filaments are reduced in size, the granu- 

 lar gland cells having sunk down, after secretion, towards 

 the structureless lamella, and not showing the swollen out 

 appearance seen in the figures. Every stage of ingestion 

 and protusion of foreign matter could be seen in the swollen 

 out endodermal bases of the mesenterial filaments, but else- 

 where was not observed. The storing up ol round, fat 

 globules, not only in the endoderm at the bases of the mesen- 

 terial filaments, but anywhere in the endoderm, indicates 

 that there must be a true digestion — due to the secretion of 

 the gland cells of the mesenterial filaments — and absorption 

 over the whole endoderm, as well as ingestion at the bases of 

 the filaments. No absorption would, however, seem to occur 

 in the mesenterial filaments, the concentration of fat, etc., in 

 the endoderm at their bases being correlated with this.* 



It is unnecessary to repeat my views on the layers in the 

 Actinozoon polyps. t There can be no doubt, if the descrip- 

 tions and figures be carefully examined, that the external, 

 tentacular, peristomial, stomodoeal and mesenterial filament 

 epithelia of /'. rnbriim all belong to the same layer. The 

 formation of the corallum, the apparent protandry of the 

 generative organs, and the presence of a distinct canal lead- 

 ing through the endoderm to the ova have already been con- 

 sidered, and require no further reference here. 



The post-larval stage in the development of the polyp, 

 which I have described above, is remarkable in many ways. 

 I have been over the anatomy many times, and I cannot see 

 that there is or can be any error in the account of its gross 

 anatomy. The main point of interest, a mouth almost as 

 large as that of the calicle, I have found also in two younger 

 stages, not however so well preserved. Such a stage is 

 absolutely without parallel among the described develop- 

 ments of the Actinozoon polyps, which, from the first, have 

 well-defined stomodoea. In the adult the stomodoeal wall 

 is ridged over the attachments of the mesenteries, and in 

 the stage described the mesenteries present are only such as 

 in the adult depend from the stomodoeum. The only logical 

 vicihod of coiiciivfiig file forniah'on of the stoniodoenni of the 

 adult to take place is to suppose that the external hody-ii'all grows 

 iWiVards^ catching up the edges of the mesenteries in its progress. 

 It finally reaches the mesenterial filaments^ which by fission 



* Tide " La Digestion chez lea Actinie.'^," by Victor "Willem, BiiU. S c. 

 Midecme de Gand, p. 295 (IS92j, and p. 375 of my paper " On the Anatomy of a 

 Supposed New Species of Coenopsammia from Lifu," iriUei/e Zool. Hesults, pp. 

 3.i7-380 aSQft). 



t Loe. cif p. 374-5. 



