256 WALTON. 



granules; he thus completes the history of the formation of the 

 refractive body. The writer has attempted to follow out the history 

 of this body in the case of A. canis and to ascertain if in that species 

 Wildman's conclusions are realized. 



Technique. 



The material used for this work was fixed in Flemming's (strong) 

 or in Carnoy's fluid. Some of the material was stained with iron 

 haematoxylin-Bordeaux red, some with Ehrlich-Biondi stain, and 

 some according to Benda's method. By these stains it was easy 

 to distinguish between the materials of cytoplasmic and karyoplasmfc 

 origin, since they took decidedly different colors. 



Origin of the ' refringent vesicles.' 



The cytoplasm of the early spermatogonia does not show any of 

 the bodies which take the blue color in Benda's stain (' karyochondria ' 

 of AYildman), but the nucleus does show numerous such particles. 

 No evidence was found, such as that given by Wildman, to show that 

 this material covered the surface of the kar\-ochromatin. These 

 separate particles were clearly distinguishable from the karyosome 

 masses and the plastosome (Fig. 1). In the older spermatogonia and 

 in the yoimgest spermatocytes, bodies staining blue like those of the 

 nucleus appeared in the cytoplasm and at the same time the number 

 of such particles in the nucleus was greatly reduced (Fig. 2). No 

 direct evidence of the actual migration of the particles from the nucleus 

 into the cytoplasm, such as shown by ^Yildman, Figure 4, to be the 

 case in A. megalocephala, was found in A. canis. Little doubt as 

 to the identity of the particles in the nucleus and in the cytoplasm can 

 be entertained, since the staining reactions of the two groups of gran- 

 ules are identical and the increase of one comes at the time of a great 

 decrease in the numbers of the other. These small cytoplasmic bodies 

 are the primitive 'refringent granules,' which are therefore nuclear 

 in origin. These bodies correspond to the ' Trophochromatin ' of 

 Marcus and the 'karyochondria' of Wildman. They swell up by the 

 accumulation of fat, thus forming the 'refringent vesicles' that are so 

 prominent, even in the living material, during the late spermatocytic 

 and early spermatid stages. 



