1070 



Fig. 2. Diagrammatic representation of the water-current inside 

 a flagellated chamber, pr. p. = prosopyle, ap. p. = apopyle. 

 The arrows indicate the direction of the current; + and — 

 refer to the water-jjressure. 



flagellated chamber must comply with definite requirements. To 

 discuss these here would take too long. 



Also in the remaining portion of the canal-system (outside the 

 flagellated chambers) there are of course a number of subsidiary 

 arrangements, which help to bring about a good circulation of water. 

 1 shall not describe these here; more especially, as they have already 

 been dealt with in detail by Vosmaer and Pekelharing, and my 

 results on this point add nothing new. 



C. The Ingestion of Food. 



Most closely connected with the problem of the water-movement 

 is that of the ingestion of food. On this question also there is a fairly 

 general agreement with Vosmaer and Pekelharing (1. c), whose careful 

 investigation showed more precisely, that the collar cells would be the 

 principal organs by means of which particles suspended in the water 

 are transferred into the tissue of the sponge, and more especially 

 into the cells of the parenchyma. Next these investigators consider 

 that the ingestion of food-particles by cells lining the canals is not 

 excluded, but that it is in any case a subsidiary method. Minchin ^) 

 holds a somewhat different view, namely that of Metschnikoff '). 



1) In Lankester's Treatise on Zoology, II, 1900. 



~) Lemons sur la pathologie comparée de rinflammation, 1892. 



