A Study of Some G'rcgarincs 17 



ing zone of the gregarines proper a clear refractive area, sharply 

 defined, and outside of this a broad, gelatinous zone. The abso^ 

 lute and relative dimensions of these coatings vary greatly ; the 

 inner coat may appear to be lacking or occasionally a cyst is with- 

 out any coating. Biitschli (1882) has noted the same occasional 

 lack of outer membranes. They are perhaps developed and sub- 

 sequently lost. 



Cyst envelopes are quite commonly regarded as secondary or 

 derived structures, which they obviously are, as there is nothing 

 in the normal gregarine comparable with the thick gelatinous cyst 

 covers. Presumably these originate in a condensation of the body- 

 mass of the gregarine and the consequent secretion of the hygro- 

 scopic material making up the cyst coverings. As might be ex- 

 pected from their mode of origin, these coverings show a 

 concentric and radial striation, the former being the more ap- 

 parent in toto observations. Sections often show an apparent 

 vacuolization of the cyst coverings where circular areas fail for 

 some reason to take a haemotoxylin stain. 



Some cyst dimensions are as follows : 



Diameter without envelopes 552 fx envelope thickness 1828 m- 



Diameter without envelopes 368 jx envelope thickness no /x 



Diameter without envelopes 460 /x envelope thickness 230 /* 



, Diameter without envelopes 166 fx envelope thickness 46 fx 



Diameter without envelopes 240 fx envelope thickness 26 fx 



The average diameter is 300-400 fx ; thickness of envelopes when 

 present 50-75 jx. 



The cysts are usually yellow, rarely orange-red, the color fol- 

 lowing directly from that of the component conjugates. On one 

 occasion four dark yellow cysts were found embedded in a 

 slightly yellow gelatinous mass, perhaps the result of conjugations 

 encysting in approximation. About the edge of the mucilaginous 

 mass were about fifty small gregarines; IMagalhaes (1900) has a 

 somewhat similar observation. 



On crushing some cysts, the contents appear rather granular 

 and not notably dififerent from the usual entocyte ; in others the 

 cyst content shows under high magnification many small bodies, 



165 



