142 



finally be usurped almost entirely by cells in the parenchyma; 

 the collar cells then become concerned only with the production 

 of the current, tlieir 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 .... I'ingestion peut se faire 

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

 tion paralt se faire généralement dans une espace annulaire situé 

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

 puissions actuellement preter (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 

 0Ü la phagocytose parait se faire avec le plus d 'énergie". 



Personal Research. — The 4 principal questions, which I 

 shall have to treat, are therefore: 1^^ Are the food particles ■ cap- 

 tured from the water by means of the choanocytes of the flagel- 

 lated chambers? 2"^- In ivhat way does this capture by the choano- 

 cytes take place? 3'd What happens to the particles captured? 

 4'^ Does the sponge dispose of still other means of capturing floating 

 particles from the tmter? 



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

 observing my normally livitig microscop)ic preparations of sponge 

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

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

 diluted 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 opened 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. 



