126 



of the movement of the isolated choanocytes^ as well as of that in 

 the intact -flagellated chambers, has shown me that the flagellar 

 motion, under normal circumstances, is in fact the same as that of 

 the Flagellata, viz. the Choanoflagellata : a spiral- or undulating- 

 motion; but that this movement, after exhaustion, very soon 

 changes into quite a different one, viz. the rowing-motion. 



The research into the motion of the flagella of isolated choano- 

 cytes was made by me in February 1915. In fact it is best to 

 be done in winter, at a low temperature. For one has to make 

 use of ravel-preparations (p. 12) of living sponge tissue, which 

 one watches as soon as possible with oil immersion in an Engel- 

 MANN case. As in winter Spongilla dies, only Ephydatia was to 

 be used for this research. 



I shall now give a description and some illustrations of the 



flagellar motion, which could be beautifully observed owing to 



the isolated situation of the choanocyte at the top of a number 



of other cells. For the observation, namely, one must have the 



flagellum isolated, but on the other hand the choanocyte itself 



may not be separated from the others, but it must, just as in 



the flagellated chamber, be fixed quite fast with its base to have 



a support against the heavy vibrations of its flagellum. I have 



noted the description literally during the observations and the 



figures were drawn immediately from the living material : 



5.55 p. m. Flagellum shows very rapid undulating-motions 



(immediately {j)rohahly in spival-Une) of small amplitude. The 



water with the particles is pushed away strongly, 



straight through the axis of the flagellar spiral, while 



at the side it flows on to the base (Fig. 56 a). 



5.57 p. m. The amplitude of the flagellar motion becomes 



much greater, the movement less quick. The water 



with the particles is still pushed on through the 



axis of the spiral, while at the side it flows towards 



the base (Fig. 56 6). 



6.00 p. m. Just a slight undulating-motion to be seen, very 



large amplitude, even less rapidity. The water with 



after 

 isolation) 



