EUPLOTES WORCESTERI: I. 



299 



of separate cilia is even more definite. Even where the memhranellas 

 appear to be ehanged only slighth' bj' the fixation, the cilia of which they 

 are composed are all perfectly distinct and separate. There are no places 

 where a few appear to be fufied in a plate, lying regularly and parallel 

 as one would expect to find if the membranellie were definite protoplasmic 

 plates. Each cilium can clearly be traced from basal granule to tip, as 

 a separate and distinct unit. The individuality of the cilia is well shown 

 by sections cutting the membranelliK above their bases. 



It may be that during life there exists a film of protoplasm joining tlie 

 cilia, too delicate to be seen, and destroyed by the slightest disturbance of 

 normal conditioiis. I have seen the sejsarate cilia of the membranellaj 

 so many times in the living animal where there seemed to be very little 

 disturbance of conditions, that I am inclined to believe that the mem- 

 branellffi of this form are composed of distinct cilia with movements so 

 perfectly coordinated that they act and ordinarily appear as a single and 

 delicate blade. Mobius also came to the same conclusion. 



The view held by the majority of zoologists is that the membranelte 

 are formed by the fusion of cilia. This Euplotes shows the individual 

 cilia better, with less fusion, than 

 the majority of other forms which 

 have Ijeen studied. Instead of ar- 

 guing from the appearances pro- 

 duced jjy certain reagents, one or 

 two structural characters, and the 

 general probaJiilities of develop- 

 ment, we here are able to see the units 

 of which the organ is composed 

 in the living specimen. This is true 

 of both adoral ^ and suboral mem- 

 branella?. 



Each membranella of the adoral 

 zone occupies the middle of a shal- 

 low groove crossing the zone. The 

 bases of the cilia of the membranellas 

 are united by a slightly elevated 

 ridge of the ectosarc. The basal 

 ridge stains more deeply than the surrounding protoplasm. At the base 

 of each membranella lies an irregularly double row of large basal granules, 

 a single grannie for each cilium. 



Cirri. — The arrangement and location of the cirri need no special 

 description, variation from that shown in Plate I, figure 1, being in- 

 frequent except for one group. The small cirri shown on the right 

 posterior margin are frequently altogether absent, and when present they 

 mav^ be either one, two, or three in number. 



Fig. 7. — Basal granules of three adoral 

 inembranellje and -^the outlines of the 

 grooves about their bases. 



