6 



continually streaming but irregularly whirling. This is, in 

 short, the theory of Yosmaer and Pekelharing. Now, I have 

 been able to establish in my living sponge-preparations that the 

 movement of the flagella, as described here, is not the normal 

 one, but abnormal, and caused by exhaustion. The real move- 

 ment takes place, just as in the Flagellata, in a spiral- or undu- 

 lating line, while the current of water in the chambers is deci- 

 dedly regular and quick (see Summary, point 20). 



6. In close relation to the problem of the water-current in 

 sponges is that of the ingestion of food — already a very old 

 matter of dispute. Here too we owe the last and principal re- 

 searches to Yosmaer and Pekelharing (1. c), by whom was shown 

 once more, that the flagellated chambers, c. q. the choanocytes, 

 would be the real „eating-organs" (Carter) of the sponge; al- 

 though both these investigators think it possible, that now and 

 then food-particles can be captured by cells lining the canals. 

 In literature this view is almost generally accepted — eg. by 

 Delage (16) 1899, Sollas (53) 1906, Biedermann (6) 1911 and 

 Jordan (32) 1913. Minchin (45) 1900, however, thinks ') that 

 in the simplest forms of sponges indeed the collar-cells represent 

 the chief „eating-organs", but that in the higher organized 

 ones the function of ingestion may be usurped more and more 

 by cells in the parenchyma (amoebocytes or porocytes). Now, I 

 myself have observed in my living preparations, that in Spongilla 

 ingestion certainly takes place by the choanocytes, but that there exists 

 still another mode of ingestion — for larger bodies only — at the 

 exterior of the flagellated chambers at the entrance of the prosopyles. 



It stands to reason, that the mode of capturing food by the 

 choanocytes was conceived in perfect agreement with the theory 

 of the water-current, as mentioned by Yosmaer and Pekel- 

 haring. So these investigators declare that the motion of the 

 flagella, by the whirling movement of the water it produces in 

 the chambers, causes, that food particles arrive easily within 

 the collars of the choanocytes and thus come in contact with 



1) Here Minchin follows Metschnikoff (44). 



