131 



tact chambers, described here. Both considered my conception as 

 convincingly proved by the preparations. 



As an exception, however, the chambers did not show these forms 

 of the flagellar motion. It occasionally happened, that after hours 

 of observation and experiment (with carmine) the movement became 

 different: a relatively very slow one, and no more the normal 

 but the same abnormal ones, which I have described in Fig. 56 h-d., 

 as being caused by fatigue and exhaustion. Accordingly, they 

 were always soon followed by entire stopping. 



Now the collars and cell-bodies of the choanocytes need treating. 

 The cell-bodies, in my living tissue preparations, were in general 

 not to be distinguished separately, as one easily understands; one 

 only sees their joined layer as a whole, round the chamber; just 

 as is given in Fig. 59. 



The collars are to be seen in great number in the chambers; 

 they are very long and leave their flagellum uncovered only for 

 rather a short part at the top (Fig. 59). (I will return to this 

 subject.) Watching a collar vertically on its longitudinal axis, one 

 never sees its apical edge ; evidently, this is so thin that it es- 

 capes to the eye. In t1iis way of a collar one only observes two 

 straight lines (the extending wall) at the side of the flagellum. 

 As there are such a great number of cells in a chamber, it is not 

 astonishing that one often has great difficulty in finding out the 

 flagellum with its own two collar-lines (of course, one immediately 

 distinguishes the former from the straight collar-lines by its 

 motion). It is quite an other case with the collars on the top 

 of which one can look ; so when our eye is in their longitudinal 

 axis. Then one sees the edge of the collar very distinctly (as a 

 little circle), in which the flagellum (as a tiny spot) (Fig. 60). Of 

 course, I could not give all this in Fig. 59 ; I, therefore, only for 

 clearness' sake have drawn the apical edge of some of the collars, 

 though in fact they can not be distinguished in this position. 



Finally I should mention that I have never observed anything 

 of the so called Sollas' membrane; this quite agrees with the 

 results obtained by Vosmaer and Pekelharing (61). 



I now still have to speak of the shape of the flagellar move- 



