Evidence from Protozoans 383 



tips, togctlicr iiiakijii; a sort of barrel-shaped collar. Tliey 

 become deeply colored when treated with nuclear stains, 

 while the fibers above described remain nearly or quite un- 

 stained. "The myophrisks do not insert, as previously de- 

 scribed, by their proximal ends into the su])erficial ecto- 

 plasmic layer, and by their distal ends into the spines, but 

 lie in the pulling fibers." ^^ 



The developmental point made out is that the myophrisks 

 arise from chromatic material lying in the central capsule 

 and migrate out to their definite positions {m.y' ., figure 26). 

 The origin takes place, according to the authors, in two 

 ways. By one method the entire nucleus of a merozoite 

 transforms into the myophrisk ; by the other, the chromatic 

 bodies of the macronuclei unite to produce these structures. 

 Numerous details are given of the development and structure 

 of the myophrisks which we can not enter into. Enough 

 is it to recognize the direct part played by chromatic sub- 

 stance in the production of these bodies. 



Now comes the point which specially concerns the pres- 

 ent discussion: The authors believe, from observations of 

 their own, that Richard Hertwig's supposition that the 

 bodies are contractile, is correct. Assuming this to be their 

 office, and assuming the authors to be right in their account 

 of the relation of the bodies to the pulling fibers and of the 

 fibers to the spines, we have here a composite apparatus 

 consisting of the spine, the pulling fibers, and the contrac- 

 tile elements, one portion of which, the contractile, is de- 

 rived from chromatic substance, and two portions, the spine 

 and the pulling fibers, are derived from non-chromatic sub- 

 stance. A slight reservation must be made in the part of 

 this statement which concerns the spine and the fibers in 

 that we are without direct observational knowledge as to 

 the oHgin of the spines and the fibers. However, it is almost 

 certain that the fibers are entirely differentiations of extra- . 

 capsular plasm ; and that the spines are at least partly of 



