Vol. XII. March, 1906. No. 4. 



BIOLOGICAL BULLETIN 



STUDIES ON THE RELATION BETWEEN AMITOSIS 



AND MITOSIS 



II. DEVELOPMENT OF THE TESTES AND SPERMATOGENESIS IN 



MONIEZIA (Continued}. 



C. M. CHILD. 



IV. The Spennatocytic Mitoses. 



The appearance of the chromosomes of the first maturation 

 division follows the stage shown in Fig. 13, A (PI. X.). Figs. 14, 

 A, 14, B, and 15 (PI. XI.) show this stage in M. e.vpansa, Figs. 

 16, A-i6, C (PI. XL), in M. pianissimo,. In the former species 

 eight of these chromosomes have been counted in the nuclei in 

 some twenty- five cases (Fig. 14, A] and in no case have more 

 than eight been found. In many cases, however, it has been im- 

 possible even with the utmost care in examining successive sec- 

 tions, to find eight, only seven or six (Fig. 14, B] being visible. 

 As regards the number in M. pianissimo, the results are less defi- 

 nite. In some cases eight (one of the nuclei in Fig. 16, C) in 

 others nine (the other nucleus in Fig. 16, C) have been counted 

 and in one (Fig. 16, B} case thirteen distinct masses of chroma- 

 tin were visible in one nucleus. This, however, was probably an 

 earlier stage for some of these masses appear to be grouped in 

 pairs. Fig. 16, A, shows two nuclei of M. pianissimo, in which 

 five of these chromosomes are visible. It was impossible to de- 

 termine whether parts of these nuclei were in the next section. 

 One reason for the greater uncertainty in regard to M. pianissimo, 

 lies in the fact that these stages were much less frequently seen 

 in my sections of this species than in those of M. expansa. I 

 believe that the utmost caution should be used in observations of 



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