632 REVIEW. 



my belief. With reference to this membrane, the descrip- 

 tions of von Lendenfeld, in contradiction to the statements of 

 Sollas and Dendy, are, I have convinced myself, as worthless as 

 those of the unique and quite different form of collar-cell till 

 very recently described and figured by him in all groups of 

 sponges. 



Dendy's observations of afferent canals lined with ectoderm 

 perforating the walls of L. stolonifera are most interesting, 

 and in my judgment probably of generic importance. Though 

 A. clathrus is much more thickly walled than most of the 

 group, the communication is established by a single perforated 

 granular cell as in other Homocoela, and strictly homologous 

 with the granular ring round a prosopyle in the Heterocoela 

 (cf. Polejaeff, Grantia tuberosa). This description does not 

 refer to other large pores which occur in this lipostomous 

 sponge, whose structure and morphology I have not worked 

 out. 



In conclusion, if in this review points of difference rather 

 than of agreement are accented, it is because the former take 

 more words to express. This paper lies throughout in lines 

 parallel to those on which 1 have been long labouring ; and it 

 may so not be impertinent to give it the cordial welcome of 

 a fellow-worker who finds a great stride made forward towards 

 the knowledge of a group that appeared almost insoluble. 



George Bidder. 



Naples; August, 1891. 



