STUDIES ON THE COMPARATIVE ANATOMY OP SPONGES. 171 



which separate the different chambers from one another, 

 roundish openings occur, which place the cavities of all the 

 chambers of a group in direct communication with one 

 another. One or several of the chambers of each group are 

 placed in connection with the central gastral cavity through 

 openings in the gastral cortex.^ Small circular inhalant pores 

 (prosopyles) occur in large numbers in the free distal portions 

 of the chamber walls. Sycantha ten ell a is said to be 

 distinguished from all other Sycons by the fact that the 

 chambers do not all communicate directly with the central 

 gastral cavity, and also by that of their non-communica- 

 tion with one another in groups, the stream of water passing 

 partly from chamber to chamber before it reaches the gastral 

 cavity. 



I am inclined to think that the apparent intercommunication 

 of the chambers may be due to an error of observation. It is 

 by no means the first time that such a condition has been 

 described. Polejaeff observes (8) that '' there is no doubt that 

 what Haeckel declares to be 'dermal ostia' and 'dermal pores' 

 in the individuals of his 'Syconusa type' were merely the pores 

 of the intercanals ; and what he calls ' conjunctive pores,' 

 these latter uniting, according to him, the cavities of the radial 

 tubes, were nothing but the common pores on the side walls of 

 the radial tubes connecting these latter with the intercanals. 

 To anyone who will notice Professor Haeckel's remark tliat 

 these 'conjunctive pores' are best to be observed in sections of 

 dry Sycones, the error into which he fell will be easily 

 comprehended." It is a noteworthy fact in this connection 

 that von Lendenfeld himself observes that his specimens of 

 Sycantha tenella had been preserved for some time in not 

 very strong spirit, so that he was unable to make any observa- 

 tions on the finer histological characters. He also refers to 

 the extraordinary delicacy of the mesoderm in all parts. 



I may also remind the reader that Carter (12) bases an 



^ Later on in the work referred to (p. 192) we are told that "jede 

 Kammergruppe ist durch eine einzige grossere Oeffnuug in der Gastralmem- 

 bran mit dem centralen Oscularrohr in Verbindung." 



