1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 373 



At first these depressions are quite small, but they elongate until four 

 of them in each group are seen to have the beginnings of three new 

 cirri in each groove. The depression to the extreme right has only 

 two cirri forming in it. The posterior cirrus in each row becomes the 

 anal cirrus. As the animal elongates preparatory to constriction the 

 depressions in which the cirri form elongate, and the nine anterior 

 cirri of each group are pulled forward to form the frontal and ventral 

 cirri. Those which are to be on the posterior animal are carried for- 

 ward nearly to the five anal cirri of the anterior daughter organism 

 and are scattered out into something near their ultimate positions. 

 Since in this description we are much more concerned with the anal 

 cirri than with the others, on account of our study of the neuromotor 

 apparatus, we shall not dwell longer on their formation since Griffin 

 has given such an adequate account. 



By the time the five new anal cirri are fairly well formed, the old 

 anal cirri have begun to be absorbed. The innermost cirrus is the 

 first to disappear and it is soon followed by its nearest neighbor and 

 so on in succession, the tM^o toward the right persisting until division 

 is well-nigh completed. Likewise the old frontal, ventral and marginal 

 cirri are absorbed and their functions assumed by the new ones. 



At first it was thought that the new depressions form in the fur- 

 rows of the original anal cirri, but this is not the case. Since the 

 original furrows are rather wide, some of the new furrows do not form 

 in them. For instance, the new furrow farthest to the right is quite 

 a distance to the right of the old furrow on that side. The furrows of 

 the anterior set, especially, bear no relation to the old furrows, but are 

 much farther apart than the old furrows in that region. Such positions 

 of the new cirri do not lend any evidence to the proposition that new 

 cirri form from old cirri. Other evidence against such an idea will 

 be suggested in a consideration of the formation of the new fibers con- 

 necting with the cirri. 



Formation op New Peristome 



The formation of the new peristome in Euplotes patella is prac- 

 tically the same as that described for E. tvorcesteri by Grifiin (1910). 

 At about the time that the micronucleus migrates from its resting 

 position to the left side of the macronucleus a slight depression occurs 

 just back and to the left of the old peristome (pi. 15, fig. 10). This 

 depression at first seems to be only in the pellicle, but it deepens and 



