416 E. L. SHAFFER. 



surround the central corpuscles (centrosomes). By a dis- 

 integration of the idiozome, the centrosomes are set free and 

 then take part in the next cell-division. In the rat, however, 

 Meves found that there is no disintegration of the idiozome, but 

 that the centrosomes wander out, leaving the idiozome intact. 

 As division progresses, the latter dissolves and disappears. 

 There is no essential difference between the "attraction-sphere" 

 of Van Beneden, the "centrosphere" of Strasburger and the 

 " astrosphere " of Fol and Boveri; and so far as I have been able 

 to ascertain, there is no fundamental difference between these 

 last named structures and the "idiozome" of Meves. One 

 thing is clear, that these structures all refer to the achromatic 

 substance of the spindle situated at the poles and usually en- 

 closing the central corpuscles. To avoid any possible misuse 

 of these terms I shall employ the non-committal term "sphere" 

 to denote this portion of the spindle. With regard to the re- 

 mains of the spindle proper, there is less confusion of terms, 

 and I shall use the term "mitosome" or "spindle remains" to 

 designate this structure. 



i. Spermatogonia. The spermatogonia in Passalus in mitotic 

 activity stand out very sharply in contrast with those in the 

 resting condition not only because of their lighter staining 

 capacity (as mentioned on p. 410), but also because they tend 

 to become round in outline and the cell walls become more 

 sharply denned. This is indicative of an internal pressure which 

 Reinke (1900) calls the "mitotic pressure." As the gonial 

 anaphase progresses, a well-defined cell-plate makes its appear- 

 ance and stains deeply in haematoxylin (Figs. 2, 24). As the 

 telophase advances, the spindle and cell-plate become more 

 compact, the former taking the acid stains and the latter taking 

 the basic stains. Fig. 4 shows several resting cells from a sper- 

 matogonial cyst with the spindle remains (mitosome) running from 

 cell to cell. Very often the spindle remains from each division 

 become so connected that they form sort of bond between all 

 the cells in a cyst. Hegner (1914) has described a similar con- 

 dition in the spermatogonial cysts of Leptinotarsa decemlineata. 

 In this case, however, he found that material fixed in Carnoy's 

 fluid always showed the spindle remains taking the basic stain. 



