32 C. ISHIKAWA. 



stage. Figs. 12 & 14 sliow a stage just after the first division : eight 

 single chromosomes are still in a single plane. Fig. 13 is the polar 

 view of the same. Fig. 16 represents a stage a little more advanced 

 than those of figs. 12 & 13. in whicli eight chromosomes lie in two 

 circles of fonr each . Fig. 15 is more advanced nnd the cell itself has 

 now begun to divide. Figs. 12-15 are drawn from specimens killed 

 with picro-acetic acid, and fig. 16 with acetic acid methyl-green. 

 All drawn by yVlI Seibert = 850. 



Figs. 17-22. — ^l^ast changes in the formation of spermatozoa. 

 Fig. 17 is just after the sec(^nd division of the s])erm-mother cell. The 

 nucleus is now fouiid to stain homogeneously. In fig. 18 a cell on 

 the left shows a vacuole in the micleus ; in the other two cells, as well 

 as in that of tig. 19, traces of chromosomes are more or less distinctly 

 to be seen. Fig. 20 shows two cells in which a big vacuole ap- 

 pears. In fig. 21 chromatic elements have become more distinct than 

 in figs. 18 (two cells on the right) and 19 : \\\Q nuclear membrane has 

 become more or less indistinct. Fig. 22 represents four spermatozoa 

 found in the vas deferens. All drawn l\y yVII x Seibert = 850. 



Figs. 23 du 21. — Represent the posterior ends of two ovaries. In 

 fig. 24 the extreme end is iiot represented, lîoth drawn by Seibert 

 VY-33. 



Fig. 26. — Two eggs just befrre the formation of the first polar 

 body. Iri both of them are seen eight dumb-l)ell shaped chromosomes 

 scattei-ed rather irregularly in the germinal vesicle. In the germinal 

 vesicle of the eo-o- on the left, a nucleolus and a number of small 

 circular bodies — -the micro- nucleoli — are seen, while in that of the 

 ^%^^ on the riglit the inicleolus is no more t(^ be seen. This figure is 

 compiled from three successive sections, y A" x Seil)ert = 330. 



/•V^.s. 26-29. — First polar spindles. Figs. M, 28, and 29 repre- 

 sent tlie side view and fig, 27 the polar view. The nuclear membrane 



