EUPLOTES WORCESTERI: II. 329 



The bottom of each slit becomes elevated in the form of a thin irregular 

 ridge which is the nidiment of the cirri which presently appear in the 

 depression. The ridge does not have the character of an undulating 

 membrane (as described by Stein and Sterki for Stylonycliia), but the 

 sliape of the depression apparently controls the form of the elevation of 

 protoplasm from its floor. The edge presents points which seem to be 

 the first indications of the cirri to be formed in a few moments, since 

 in the few instances which I have been able to observe the number of 

 points on the ridge coincided with the number of cirri to arise from 

 that particular depression. Wallengren finds that each cirrus of E. harpa 

 arises independently of the others in the same slit, and that there is no 

 indication of an undulating membrane, or a protoplasmic ridge such as 

 I describe, preceding the appearance of the cirri. He also observes the 

 posterior cirrus of each group to appear first, followed in succession by 

 the more anterior ones. So far as I have been able to observe, all the 

 cirri of a group arise at the same time in E. worcesteri, although it 

 is true that the posterior one of each group outstrips its .fellows in 

 growth from the very first. 



The early development of the cini must jDroceed very rapidly, for the 

 stage in which the depressions only exist is very rarely seen among large 

 numbers of dividing individuals. Specimens like figures 25 or 33, Plates 

 VI and VIII, are common enough. 



Three cirri arise in each depression, except in the one at the left of 

 each row where but two appear. From the fourteen cirri thus appearing 

 in each row are formed all the frontal, abdominal, and anal cirri of each 

 daughter body, except one. The history of this last cirrus is peculiar, 

 and is different in the two bodies. That of the anterior body (F) 

 appears to the left of slit A, just behind cirrus 7, usually as is shown by 

 figure 25, Plate VI. The corresponding cirrus of the posterior body (/) 

 springs from the medial wall of the peristomial invagination, just within 

 the aperture and immediately after its permanent opening. Neither of 

 these cirri arises from a depression like the others. 



The left marginal cirri of the two bodies also arise from depressions 

 to the right of the old and new peristomes. (L M, I m, figures 32, 25, 

 and 33.) The development of the left marginal cirri resembles that of 

 the ventral cirri. 



As the cirri of groups A, B, C, D, E, a, b, c, d, and e grow, the 

 depressions in which they arise also increase, particularly in length. 

 (Plate VI, figure 25, and Plate VIII, figure 33.) The enlargement of 

 the grooves a, 6, c, and d causes the effacement of the anterior portions 

 of the original grooves of the anal cirri I to IV, while the portions left, in 

 which the anal cirri still stand, are directly behind the new grooves, 

 separated from them only by narrow oblique ridges. (Plate VIII, figure 

 33.) The remnants of the old grooves are effaced very soon after this 



