A Study of Some Grcganncs 13 



tance equal to its own length, that G. municri or H. rigida require 

 half an hour to fravel i cm., and that the faster white gregarine 

 can only make it in a little over eighteen minutes, it seems evi- 

 dent that one need not ask for violent muscular displays to ex- 

 plain this. 



The method by which I believe muscular activity to be trans- 

 mitted to a surface is practically stated in this sentence from 

 Crawley (1905), "A given point on the gregarine's surface 

 pushes backward and transversely upon whatever may be in con- 

 tact with it.'' In other words, the gregarine "sculls" in the same 

 manner that a skater does, converting the transverse impulses of 

 the myocyte fibers into a rectilinear movement. And where the 

 transverse impulse of the skater is resolved through two skate 

 blades, the gregarine impulse is resolved through the surfaces of 

 the numerous cuticular lamellae or ribbings ; where the sharp 

 skate blade cuts into the ice for its leverage, the cuticular rib- 

 bings get a leverage from the sticky substance which Schewiakofif 

 (1894) regards as secreted bv all gregarines (though some cer- 

 tainly lack not only a "Gallertschicht" but a sarcocyte as well), 

 and Crawley regards it as at times secreted by the gregarine and 

 in other cases derived from the broken-up host tissue. 



In the case of the exceptional gregarine forms with a tuber- 

 culate cuticle some suitable modification of the sculling move- 

 ment probably occurs. That the cuticular markings should be 

 associated with progression is not at all remarkable. There are 

 many things pointing to the ciliates as the ancestors of the 

 gregarines (7'idc Calkins. 1901) and some reason to suppose that 

 the cuticular markings are homologous to the cilia and perhaps 

 derived from them. 



The entocyte is regularly clear and transparent in young spec- 

 imens and shows a fine to slightly coarse granulation. In older 

 specimens it becomes opaque, a common thing in gregarines, 

 owing to the storage of reserve food particles, and takes on a 

 yellow color. Occasional specimens show yellow drops of vary- 

 ing size in a clear peripheral area where the oil reserve, normally 

 distributed somewhat evenly, has broken upland permitted the oil 

 to collect in drops. The larger granulations of the entocyte may 



161 



