THE RELATION BETWEEN AM1TOSIS AND MITOSIS. 1/9 



A-6, B, PI. VIII., 7, A-S, B, PI. IX.) are taken from the chrom- 

 oxalic preparations and cell-boundaries do not appear in most 

 cases though they may be present. Fig. 9, D (PI. IX.) is taken 

 from a sublimate preparation at a rather late prespireme stage 

 and shows the cells as distinct. 



But for present purposes the nuclei are of chief importance. 

 Figs. 5, A$, C (PI. VIII.) represent stages just after the forma- 

 tion of the membrane. In Figs. 5, A, and 5, B, amitoses are 

 visible and in Figs. 5, B, and 5, C, two of the very infrequent 

 cases of mitosis in these stages are shown. Figs. 6, A, and 6, B 

 (PI. VIII.) are from slightly later stages : Fig. 6, A, is a section 

 through one side of a testis and does not show the full size. 

 Both figures show amitoses and Fig. 6, B, shows one case of 

 mitosis. Figs. 7, A, and 7, B (PI. IX.), are from still later 

 stages. In the latter figure one case of division of a nucleus 

 into three parts is shown. The nuclei in which such divisions 

 take place are usually larger than the others, often lie near the 

 center of the testes and are similar in appearance to the large 

 nuclei along the axis of the developing ovarian follicles which 

 were mentioned in the preceding paper. In Figs. 8, A, and 8, B 

 (PI. IX.), stages just preceding the first appearance of the spireme, 

 each with several amitoses, are shown. In Fig. 8, A, one of the 

 large nuclei dividing into three parts is seen near the opening of 

 the vas efferens. 



In Fig. 9, A-Q, D (PI. IX.), cells or cell-groups from various 

 stages containing amitoses of special interest are shown. Figs. 

 9, A, and 9, C, represent cases of the form of amitosis designated 

 endogenous in the preceding paper in which the two nuclei result- 

 ing from division do not occupy the entire space within the old 

 membrane. Numerous cases of this sort have been observed in 

 the testes and have been examined with great care. Fig. 9, B, is 

 a case of triple division and Fig. 9, D, a case of cytoplasmic divi- 

 sion proceeding from within outward. This figure is from a sub- 

 limate preparation. 



During these stages mitoses are rare. Very often not a single 

 case is found in any of the numerous testes of a proglottid. In 

 other proglottids a number of testes may show one or more each. 

 In general the relative frequency of mitosis appears to vary in 



