B. Porifera incalcaria. III. Cornacuspongiae. 7 



revetante, et massive on raphyroTde . Also the spicules vary immensely, and 

 only tro. ac. never fail. Neither length nor diameter are constant; large speci- 

 mens generally possess large spicules. - There are 4 cell-types: contractile, 

 flagellate, connective and digestive (pigmented) . To the first belong the epithelial 

 cells, the fibrous cells and what generally are called contractile mesoderm-cells. 

 These are all considered to be modifications of one and the same type. Ova are 

 found in September and October. They change shape like an Amoeba. The spi- 

 cules are sometimes united together by a yellowish horny mass, which however 

 does not appear to be spongin, but an accidentally thickened ground substance. 

 There are two kinds of papillae; one bears oscules, the other pores; but some- 

 times there are pores around an osculum on one and the same papilla. If a boring 

 form does not find a suitable place or sufficient space, it begins to cover the sub- 

 strate. Very strong specimens may then become quite massive, and such forms 

 were known and described as Raphyrus griffithsii. This was originally suggested 

 by Johnston, but Bowerbank, Schmidt, Gray a. o. separated the two, till Carter 

 again identified C. celata and R. griffithsii, apparently however, without being 

 believed by anybody. C.vastifica and C.northumbrica of Hancock are only one 

 species. They show reproduction by gemmulae, and such gemmulae are met with 

 also (S 2 ) in Suberitcs domuncula, where Carter described them as ova (Ann. Mag. 

 N. H. (5) Vol. 12), and in S.faus. The boring is probably not effected by any 

 acid. T. concludes that the boring sponges do not belong to any special group, 

 but that they are weritables Corticatae. 



Thomson gives some anatomical details of Suberites domuncula. Vosmaer's state- 

 ments on the epithelium and the canal system are confirmed. The connective 

 tissue exhibits great variety of composition in different regions . Strands of 

 fusiform cells are found just below the ectoderm, in the region adjoining the shell 

 on which the sponge grows, and frequently round the larger canals. They are to 

 be considered as muscle-cells. S. domuncula appears to be hermaphrodite. 



Dendy characterises the genus Ridleia as follows : Sponge corticate, with a 

 highly-developed system of fibrous tissue. Consisting of a single solid body ter- 

 minating above in an osculum, which leads into a well-defined oscular tube with 

 fibrous walls. Spicules monactinal, styli or tylostyli, confined almost entirely to 

 the ectosome. Skeleton composed chiefly of stout longitudinal bands of spicules 

 situated in the inner portion of the ectosome, and of tufts of small spicules pro- 

 jecting at the surface of the sponge. Canal system canalicular, flagellated cham- 

 bers diplodal. R. is closely allied to Quasillina ; externally they ressemble each 

 other much. The chief difference is 1) that the canal system of the former is 

 canalicular, while the latter has a lacunar canal system; 2) that the fibrous tissue 

 in the former is largely developed and almost absent in the latter. A re-exami- 

 nation of the anatomy of Q. led to an almost complete confirmation of what 

 Dr. Vosmaer has already published . 



III. Cornacnspongiae. 



According to Zalacostas. spongin chemically is very near to the collagenous 

 matters. 



A. Halic ho ndrina. 



See Sollas (S 2 ), supra, p 5. 



Noll describes Desmacidon bosei n. The skeleton consists of bundles of tr. ac.. 

 kept together by spongin. Besides are found: co of various shape and size, and 

 rut 2 . There is a central canal in all the spicules, and around them an organic 



