g3Q Theophilüs s. Painter, 



elements. The meaning of the variation of the accessory chromosome 

 is made clear by the cell shown in Fig. 35. Here the ctetosomes 

 are attached to the accessory body a fact that gives us the quadri- 

 partite form, and also explains the inequality of length of the two 

 elements of the accessory chi'omosome, shown in Figs. D and 37. 

 In the latter case the ctetosomes are apparently fused wdth the 

 accessory chromosome elements, while in such cells as are shown in 

 Figs. C or 35, they appear separated from them. It is very 

 interesting to note that these two types of primary spermatocyte 

 cells are equally as numerous in the testis, and we have here con- 

 clusive proof that the ctetosomes we unequally distributed to the 

 primary spermatocytes in the last spermatogonial division. 



The ctetosomes pass undivided to one pole of the cell with the 

 accessory chromosome. Part of the secondary spermatocyte cells 

 which carry the accessory chromosome will also contain the former 

 elements. I have not been able to follow the course of these small 

 bodies in the second division in any detailed way. We may find 

 them in the spindle where they are seen best in equatorial view, 

 but it has not been determined whether or not they divide. Judging 

 from another form, it seems probable that the ctetosomes do divide 

 at this time, and the fact that they do not lag behind in the spindle 

 would seem to indicate this also. It is interesting to note that 

 during this division the ctetosomes do not show any relation to the 

 accessory elements. The latter bodies divide early in the metaphase 

 and each spermatid receives the two rod like elements which con- 

 stitute one dose of the accessory chromosome. 



The sperms then are dimorphic, as regards the sex chromosome, 

 as was shown by Beeey and Wallace. 



Autosomes. 



In Figs. E, F and G, are shown some of the chromosomes which 

 are found during the early prophase of the first maturation division. 

 We may conveniently distinguish two general types: a) autosomes 

 made up of two rods attached at one end forming V-shaped bodies, 

 b) autosomes made up of rods attached at the two ends but free 

 in the middle. 



The way in which these chromosome elements separate during 

 the mitosis is shown in Figs. H, I, J and K. It is evident that tiie 

 division of the V-shaped elements amounts to a separation of the 

 two arms of the V, as shown in Fig. H, while in the case of the 



