EUPLOTES WORCESTERI: I. 301 



converging until the}^ end close to each other at the anterior extremity of 

 the ventral surface. Occasionally they seem to uuite as descrilDed by 

 Maupas, but I do not find this condition so frequently as the other. 

 These fine fibrils are much larger and more readily seen than the fibrils 

 of the other cirri. I have never seen in one specimen so many filjrils 

 as Prowazek shows in his figures of E. harpa. The fibrils of the anal 

 cirri are seen easily in the living animals, and they become quite con- 

 spicuous after staining with aceto-carmine. They are not as easily seen 

 in sections, because of the difficulty of cutting sections exactly parallel 

 with their course. 



Plate II, figure 4, represents the fibrils seen in a living animal; text 

 figure 9 shows others seen after fixation, but without staining. Plate III, 

 figure 8, is a drawing of a section stained with iron-hgematoxylin. 



From these figures it will be seen that the fibrils could not be traced 

 from the base of every cirrus^ and that different arrangements were found 

 in difl:erent specimens. In general it may be stated that the fibrils 

 seemed to be most developed in connection with the strongest or most 

 used cirri. 



The fibrils lie just inside the ectosarc, or it might be better to say in 

 the inner layer of ectosarc. Each ends in the basal plate of dense 

 protoplasm under the cirrus. They appear to be round in cross-section. 



It also will be noticed from the figures that more thap'one fibril is 

 connected to several of the frontal and abdominal cirri. I have never 

 seen mor(* than the single filjril for each anal cirrus. If the fibrils are 

 contractile, as seems altogether probable, they are developed around the 

 bases of the cirri in such directions as to assist in producing the ordinary 

 motions. As the anal cirri have only a single strong motion, a vigorous 

 kick directed backward, each needs but a single strong fibril. The 

 movements of the other cirri are more varied and consequently the 

 fibrils are more numerous. It may be that such fibrils are connected 

 with all the cirri, but only a few are visible in any specimen; or it is 

 possible that the ordinary contractility of the ectosarc is sufficient to 

 produce the movements of the smaller cirri and that no specialized filjrils 

 exist. 



In this connection the fact may be mentioned that the two left 

 marginal cirri . (back of the peristome) do not have the striking or 

 kicking motion of the others, but lash rapidly and forcilily with a spiral 

 motion. 



Bngelmann noticed that a very fine ijlasma-thread arises from each 

 marginal cirrus of Stylonichia, which can be followed close to the ventral 

 surface nearly to the mid-line of the body. Maupas repeated this obser- 

 vation and also discovered the fibrils of the five anal cirri of Euplotes. 

 The anal cirri of Stylonichia possess similar fibrils. Engelmann sug- 

 gested that the fibrils were nervous in function, radiating from a common 

 nerve center, but Biitschli believed them to be similar to the intracellular 



