328 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



and placed in the skin of a Ceraosponge, with the points centri- 

 fugally as weapons of defence. (Von Lendenfeld, Neue Aply- 

 sinidee.) 



4. Digestion. 



This most important subject is unfortunately also one of the 

 most difficult to investigate. Experiments with carmine-feeding 

 nd other observations seem to show that the digestion is intra- 

 cellular. The carmine particles are taken up freely by all 

 Epithelia of the Sponge, but they are soon ejected from all the 

 cells except those which cover the introductory canals. 



These cells do not eject all the carmine at any rate, but pass 

 some of it on to the wandering cells which carry it about, 

 dissolve some of the substance (the angular particles loose their 

 sharp edges), and finally seem to pass it on to the cells of the 

 ciliated chambers. 



Whether the Sub-dei-mal cavities and introductory canals really 

 are the digestive cavity as I believe, or not, cannot yet be known, 

 (von Lendenfeld, Neue Aplysinidae), although my experiments 

 have convinced me of the high probability of it. 



The cells of the ciliated chambers are in my opinion to be 

 excluded from all functions which have to do with the taking up 

 of nourishment. (Polejaeff Challenger-Calcarea.) 



Excretary functions and breathing. 



I assume (von Lendenfeld, Neue Aplysinidse), that the cells of 

 the ciliated chambers are the excretary elements, that they act as 

 kidneys, and I am also enclined to believe that through them the 

 exchange of oxygen and carbonic acid is effected. Their shape, 

 and also other observations point that way. The wandering cells 

 transport the chemical substances which are either necessaiy for 

 the organism or superfluous to the places where the former are 

 wanted and the latter ejected. 



