140 



say that tho choanocyt(3S really are the organs by wliich particles 

 suspended in the water, passing the canals, are captured and thus 

 brought into the tissue of the body". 



It is a matter of course that Vosmaer and Pekelharing 

 concoived the mode of capturing food by the choanocytes in 

 perfect agreement with their theory of the water-ciirrent, which 

 theory I mentioned at large on page 123 — 124. So the investigators 

 say: „The particles (suspended in the water) are.... transported 

 to the flagellated chambers ..... here the regular current at 

 once changes into a very irregular niövement" (as in Fig. 58&). 

 „The particles are moved to and fro in the chamber, and though 

 they partly leave the chamber through the apopyle, a number 

 will, however, arrive ivitJdn ') the collars of the choanocytes. 

 The protoplasm of the cells then seizes the particles in order to 

 give them off again to the cells of the parenchyma. This does 

 not prevent that now and then particles can be seized by cells lining 

 the canals; but this will always be of less importance. Met- 

 schnikoff's opinion that the flagellated chambers were not the 



real „eating-organs" is not sufficiently supported by his 



observations". 



Thus runs the theory of Vosmaer and Pekelharing. Minchin 

 (45) 1900 holds a somewhat different view, namely that of 

 Metschnikoff (44) 1892. Although this theory of Metschnikoff 

 has been contested by several investigators — eg. by Yosmaer 

 and Pekelharing — and Biedermann (6) declares: „diese letz- 



tere Bchauptung" (the Metschnikoff theory) „erfuhr keine 



Stütze, indera sich herausstellte, dass die Kragenzellen wirklich 

 die einzigen direct nahrungsaufnohmenden Elemente sind", I 

 shall quote Minchin's words, as they become of importance by 

 the results of my research. Minchin says: „Although the problem 

 might seom a simple one, thcre is no question which has been 



so much discussed as the nutrition of sponges With regard 



to the ingestion of food two opposite opinions have prcvailed, 

 one set of investigators attributing an ingestive function to the 



1) J talies from me, v. T. 



