302 GRIFFIN. 



fibrils of ciliated metazoon cells, and probably contractile; this is much 

 the more reasonable view. Every detail of arrangement and structure 

 indicates that the fibrils are, principally at least, contractile in function. 

 A relation with the myonemes of other Ciliata suggests itself imme- 

 diately ; and, if each cirrus represents the highly developed and specialized 

 remnant of several rows of cilia, it seems possible that some of the 

 myonemes of these rows^inay have remained and developed accordingly. 

 The objection to this theory is twofold: first, that many of the fibrils 

 run in directions which bear no relation to the hypothetical original 

 ciliary rows ; and, second, that while each cirrus has several rows of basal 

 granules, the fibrils do not correspond to these rows. 



Sensory bristles. — The flypotricha are commonly described as having 

 nmufvous immotlTe bristles on the dorsal surface, which probably are the 

 modified vestiges nf a once close ciliation (see Biitschli, Doflein, et al.). 

 A sensory function is ascribed to them, and the name of sensory bristles 

 will be adopted here without questioning the correctness of its application. 



I find that JEuplotes worcesteri possesses not only the usual dorsal 

 bristles, but also several rows and definitely arranged groups of ventral 

 bristles. The bristles of this Euplotes are extremel}- short and trans- 

 parent, rendering direct observation most difficult ; but as the base of each 

 bristle is usually surrounded with refringent ectosarcal granules, their 

 positions can easily be seen. Plate II, figure 3, is drawn from a specimen 

 in which the bristles were unusually clear. The tips were bluntly pointed, 

 while the bases were expanded. The shape is decidedly different from 

 that of the bristles heretofore described in various Hypotricha by. other 

 observers, and from the bristles of other species of Euplotidse which I 

 myself have obse^^-ed. The bristles of the ventral surface are even smaller 

 and more difficult to observe than tlie dorsal ones. I find no record of 

 any |)i'evious observation of these ventral sensor}^ biistles, although 

 Stein saw the granules which surround their bases along the sides. of the 

 adoral zone of membraneU^e in Eioplotes charon, 0. F. M. These obser- 

 vations have been repeated many times, and careful examination has 

 been made on, numerous occasions to determine that a bristle stood at the 

 center of each group of granules. As the granules are so easily seen, and 

 the bristles are distinguished only with difficult}'', there was manifestly 

 some danger of assuming that each group of granules necessarily indicated 

 the jDosition of a bristle. The bristles of the dorsal surface usually lie in 

 eight longitudinal rows, although six, nine, or ten rows are found. It 

 happens that Plate II, figure 3, is drawn from the only specimen I have 

 ever seen having six rows* 



Upon the ventral surface the bristles are always arranged as follows : 

 First, there are several bristles about the base of each cirrus ; usually 

 four, occasionally six, at the bases of the large ciiTi, and two or three 

 beside the smaller ones. (Plate II, figure 4.) Second, there is a row of 

 bristles on each side of the adoral zone of membranella? ; with few 



