320 DR. G. P. BIDDER : NOTES ON THE 



accumulate in the chambers under these conditions is composed of such 

 cellular excreta. And, as Vosmaer and Pekelharing point out (1898 5, p. 10), 

 the " clods of detritus " are many times larger than the prosopyles, and 

 consequently could not have entered through the prosopyles, but must 

 necessarily have been formed within the chambers. 



Add that, in such sponges, I found in life that " almost every cell possessed 

 a globule containing angular dark particles/' sometimes, as in (1895) fig. 4, 

 " projecting on the surface between collar and flagellum. These globules 

 were observed and drawn moving in the distal protoplasm of the cells ; " 

 (Note Gr) " there were numerous bodies of similar appearance (cf. fig. 13 a) 

 floating freely in the chamber " (1895, p. 18). The figures illustrating this 

 statement lost detail in their reproduction ; those appended here are on the 

 full scale of the sketches (fig. B enlarged to the scale of figs. A and C). 

 They are corroborated by Cotte's observation (1903, p. 559), in a Sycon 

 raphanus which had absorbed tournesol, of two blue spherules (each containing' 

 a darker blue point) being ejected by choanocytes ; the spherules being 

 thrown out from the annular space between flagellum and collar. 



In regard to the gelatinous matrix of the feces, " I have often suspected, 

 from paraffin sections, that the food vacuoles of sponges are filled with some 

 gelatinous matter, coagulated in preservation " (1895, p. 18). Cotte (I.e.), in 

 Reniera simulans fed with carmine or lamp-black and returned to clean water, 

 observed afterwards " des bols f^caux " in the flagellate chambers". " La 

 substance hyaline qui agglutine les corpuscules solides indique vraisemblable- 

 ment qu'il y a eu ingestion prealable par les choanocytes, et que les 

 choanocytes les ont ensuite abandonnes." Greenwood and Saunders (1894, 

 p. 449) describe a type of digestion in Mj'xomycetes where " any nodule of 

 food as yet unchanged is invested by a homogeneous mucilaginous sphere, or 

 in later stages .... a viscid mould or cast of the interior of the vacuole 



o 



is formed" . . . . " We think that some element present is not only un- 

 dissolved but insoluble, and comparable probably to that mucilaginous 

 residue which gives so distinctive an appearance to the egesta of many 

 Infusoria." Discussion with Miss Greenwood greatly influenced my con- 

 clusions. 



It is interesting that Dendy's description, quoted above, verifies the old 

 observation of Carter (1849, p. 98) that the " faecal matter " issuing in the 

 oscular current is markedly heavier than water. It has been suggested to 

 me by a friend that this may indicate the deposit of calcium salts in the 

 fsecal boli, and that to these may be in part due the refractive or opaque 

 granules which characterise the boli. In any case, I venture here to repeat 

 from another standpoint the comparison which Dendy made between these 

 cellular faeces in the flagellate chambers and the "masses of granules" 

 figured as spermatozoon-heads by Polejneff and other authors. If the sign 

 of completed digestion in the collar-cell be the complete replacement of the 



