290 NATHAN FASTEN. 



makes its appearance. Sometimes two clear openings (Figs. 

 48-49, v) may be seen, but these later flow together into a single 

 one (Fig. 50, v). At the same time the mitochondrial mass 

 wanders in between the nucleus and the vacuole (Figs. 48-52, 

 wi), and ultimately fills this entire space (Fig. 53). The centro- 

 some increases somewhat in size and takes a position in the center 

 of the mitochondrial mass (Figs. 50-53, c}. 



The mitochondrial mass now transforms into a ring resembling 

 a doughnut, and the centrosome comes to occupy the center of 

 its inner open space (Figs. 53 and 54, c). The upper portion of 

 the nucleus also becomes located in this space (Figs. 54-58, n). 

 At the same time, the karyosome-like body, situated within the 

 center of the nucleus (Figs. 47-53) migrates upward to the middle 

 of the upper portion of the nucleus (Fig. 54) until it comes to lie 

 directly below the centrosome. 



Binford ('13) in describing the transformation of the spermatids 

 of Menippe mercenaria claims, on p. 156, that "after the mito- 

 chondrial ring is completed the nucleus becomes widely separated 

 from it and the capsule (Figs. 50 to 52). This, however, is not 

 always the case. In two preparations from which Figs. 33 to 35 

 and 37 to 43 were drawn, the nucleus remained fitted closely on 

 the capsule as shown in Fig. 43. As the two different conditions 

 were obtained with the same fixing fluid it is hardly probable 

 that the difference was caused by the fixing." -In sections of 

 testicular material of Cancer magister, a few of the transforming 

 spermatids showed the conditions which Binford describes, but 

 in smear preparations not a single such instance was discernible. 

 I therefore suspect that Binford had to deal with defects which 

 are often produced in cytological material which is prepared by 

 the fixation and the sectioning methods. 



Simultaneously with the last-mentioned changes, a second 

 vacuole (Fig. 54, v'), makes its appearance in the anterior ex- 

 tremity of the original first (Fig. 54, v), or primary vacuole. 

 At first this second vacuole looks like a small bubble of liquid 

 which stains rather darkly with Heidenhain's haematoxylin. 

 It soon increases in size, becomes more distinct (Figs. 54-57, v'), 

 and stains somewhat lighter. It is quite evident that Binford's 

 ('13) so-called "inner tubule" formed during the spermatid 



