511 



although not confined entirely to it, is a somewhat simpler process 

 in which the chromatin gathers around some three-fourths of the peri- 

 phery of the nucleus forming a conspicuous crescent which becomes 

 denser and narrower as the process continues. The nuclear membrane 

 thins out along the margin free from chromatin and ultimately fades 

 away in this region leaving the spermatozoon head as a horseshoe- 

 shaped loop in the cytoplasm. Some of the nuclei of the smaller type, 

 however, may follow more nearly the course figured in the plate. The 

 two processes do not seem to be essentially difi"erent. 



Fig. 39 represents a camera lucida drawing of two spermatozoa 

 which happened to lie side by side in a smear preparation. It is 

 evident that they are of pronouncedly different size. Furthermore, it 

 was found that two sizes of spermatozoa appear constantly in various 

 preparations. There is considerable fluctuation in the size of individual 

 spermatozoa, but from a series of comparative measurements, made 

 by means of an eye-piece micrometer, it appears that there are two 

 means about which the fluctuations take place which stand in the 

 relative proportion of approximately seven to ten. Judging from the 

 course of the tranform ations of the spermatids together with the size 

 of the mature spermatozoa it seems legitimate to conclude that the 

 larger spermatozoa come from spermatids which contain the odd 

 chromosome. 



The finer details of structure in the spermatozoon head were not 

 as readily observed as in the pigeon. In especially favorable prepara- 

 tions, however, by careful focussing there were to be seen a series of 

 more highly refractive transparent areas as indicated in Fig. 40. These 

 were too vaguely visible to be counted with certainty although the 

 number is not less than eight and is probably slightly greater. 



As regards the determination of sex and its connection with the 

 odd chromosome, the question has been so repeatedly and so fully 

 discussed in recent literature that it would be superfluous to discuss 

 it anew beyond pointing out that in the guinea we have a condition 

 which seems to parallel most strikingly, as regards the odd chromo- 

 some, the conditions found in many of the insects. Inasmuch as full 

 bibliographies^) concerning the whole question from the cytological 



1) For extensive bibliographies see the following papers: E. B. 

 Wilson, Studies on Chromosomes. Journ. of Exp. Zool. Vols, for 1905, 

 1906, 1907, 1909. — Alice M, Boring, A Study of the Spermatogenesis 

 of Twenty-two species of the Membracidae, Jassidae, Cercopidae and 

 Fulgoridae, with special reference to the Behavior of the Odd Chromo- 

 some. Journ. of Exp. Zool., Vol. 4, 1907, No, 4. — Fernandus Payne, 



