142 



finally be usurped almost entirely by cells in the parenchyma; 

 the collar cells then become concerned only with the produetion 

 of the current, their ingestive activities being in abeyance (Met- 

 schnikoff)." 



Thus MiNCHiN. Finally I will just mention what Cotte (12) 

 1902 says about the mode of ingestion of food by the choano- 

 cytes: „je suis disposé a croire que..,, l'ingestion peut se faire 

 par toute la surface de la cellule active". But further: „L'inges- 

 tion parait se faire généralement dans une espace annulaire situé 

 entre Ie flagellum et la collerette". And „Le seul róle que nous 

 puissions actuellement prêter (aux coUerettes) en dehors d'une 

 intervention active dans les faits de phagocytose, est celui de 

 guider les particules alimentaires vers la base du flagellum, point 

 oü la phagocytose parait se faire avec le plus d'énergie". 



Persoiial Research. — The 4 principal questions^ wkich I 

 sïiall have to treat, are therefore: P^ Are the food particles cap- 

 tured froni the water bi/ means of the choanocytes of the fagel- 

 lated chambers? 2'^^, Jn wJiat ivay does this capture by the choano- 

 cytes taJce pjïace? 3''^ What happe^is to the particles captured? 

 4^^ Does the sponge disp)0se of still other means of capturing fioating 

 particles from the water? 



I have been able to answer these 4 questions, ainong others by 

 observing my normally living inicroscopic p)reparatio7is of sponge 

 tissue (p. 12 — 13). I therefore placed these preparations in water 

 from the conduit, to which I added some carmine, or in a very 

 dilutcd suspension of green symbiotic algae isolated from another 

 sponge. To make the observation succeed, it is necessary to trans- 

 port the preparations already some hours in advance into the 

 glass vessel (with the suspension) finally used for microscopising, 

 otherwise one never sees the capturing of the particles; for, pro- 

 bably, the ostia remain closed after the transport of the sponges, 

 to be opcnod only after some time, so that only then the normal 

 water-circulation starts. The phenomena can never be observed 

 so beautifully with a suspension of symbiotic algae as with a' 

 carmine suspension. 



