CILIATE FIBRILLAR SYSTEMS 



209 



careful analysis of the finer structure of their fibrillar system, so far as 

 I have found, is that of G. Entz (1893) on "Die elastischen und con- 

 traction Elemente der Vorticellen." In the brief review here presented 

 of this system, I have followed chiefly this excellent account. 



In this review of the fibrillar system of Vorticella and its relatives, 



Figure 75. Stalk of Zoothamnium arbuscula. (Entz, 1893.) 

 axo. — Axonem cyt. — Cytophane spr. — Spironem sps. — Spasmonem 



it will be more convenient to consider first the fibrils of its contractile 

 stalk, then those of its body and its peristome. 



Previous to the critical investigations of Entz (1893), the "Stiel- 

 strang" in the contractile stalk of the vorticellids, which had been 

 identified by Ehrenberg (1838) as the "Stielmuskel," was found by 

 later analysts to be composed of two parts: (1) the "Stielmuskel," a 

 cylindrical, or band-like, strongly refractive fiber, and (2) an adjacent, 

 granular "Protoplasmastrang," which accompanied the former through- 



