I5O FERNANDUS PAYNE. 



the number or arrangement with certainty. This difference, 

 however, could be easily accounted for by a difference in fixation, 

 as I have noticed the same. thing in regard to the tetrad group 

 in Sinea. As he found 32 chromosomes in the spermatogonia, 

 Montgomery thought that the four small ones divided equally 

 in both divisions, and he figured them as dyads attached to the 

 plasmosome during the growth period. I have no evidence to 

 offer to the contrary, but one thing comes out clearly in a study 

 of the growth period, and that is that the four small chromatin 

 bodies which Montgomery calls " chromatin nucleoli," show no 

 appearance of being bivalent, and that they are not merely in con- 

 tact with the plasmosome, but are actually embedded in it (Fig. 

 n, ). In the prophase of the first division (Fig. n, F), the 

 plasmosome breaks down and the small chromosomes remain, 

 but even here they do not appear to be bivalent. 



In comparing Fig. n, E and F, with Fig. 6, M and N, the same 

 stages in Silica diadcnia, we notice a striking similarity. As the 

 four small chromosomes embedded in the plasmosome in Sinea 

 are univalent, is it not also possible that the same is true in 

 Acholla? In the light of the present discoveries, it seems de- 

 sirable that the form be reexamined. 



In order to summarize briefly the results, I have made a 

 diagram (Fig. 12) illustrating the four different types of chromo- 

 some distribution described in the present paper. I have omitted 

 from the diagram the type described in Acholla multispinosa as 

 my evidence is hardly conclusive. The differential chromosomes 

 are in each case made in black, while the remaining ones are left 

 in outline. The size relations of the differential chromosomes 

 are maintained as nearly as possible. In the first column to the 

 left, are the metaphase figures, polar view, of the first division 

 in each type. In the second column are side views of the second 

 division, anaphase, showing the manner of separation of the 

 dyad, triad, tetrad and pentad groups of differential chromo- 

 somes. The third column gives the two classes of spermatozoa 

 produced in each type; the fourth, the reduced number of chro- 

 mosomes in the egg (inferred) ; and the fifth, the end result pro- 

 duced by the fertilization of the egg by the two classes of 

 spermatozoa. 



(To be continued.) 



