24 J- E. WODSEDALEK. 



types of abnormalities we have cases of scattered chromosomes 

 which do not enter into the spindle at all (Figs. 16-36). Guyer's 

 suggestion regarding the curious fact that the multipolar spindles 

 seem to be confined largely to the primary spermatocytes prompts 

 one immediately to associate the fact with the pseudo-reduction 

 or formation of bivalent chromosomes which occurs normally at 

 this stage of spermatogenesis, is considerably strengthened by 

 the results of this investigation on the mule, since a thorough 

 study of the entire phenomena of pseudo-reduction was possible 

 in this hybrid. 



The diverse types of multipolar spindles and other abnormal- 

 ities that occur in the primary spermatocytes of the mule are 

 shown in Figs. 16-36. Fig. 16 represents a polar view of a 

 metaphase stage. Twenty-eight chromosomes, some bivalent 

 and some univalent, can be seen in the equatorial plate, while 

 sixteen all apparently univalent, together with the accessory are 

 scattered about in the cytoplasm. Fig. 17 shows a meager 

 attempt at spindle formation. A bunch of chromosomes is 

 found at the equatorial plate and only a few spindle threads 

 could be seen and those appeared to be broken up. There was 

 no sign of the centrosomes being present. The other chromo- 

 somes, both bivalent and univalent, are scattered about. The 

 cell was no doubt in the process of decay. A trivalent chromo- 

 some can be seen at the lower part of the figure. Trivalent 

 chromosomes are not uncommon but the three components 

 can seldom be seen at this advanced stage. They usually fuse 

 together, forming a large chromosome, frequently spherical in 

 shape. Especially is this true when the cell is in the process 

 of deterioration. The large spherical body at the upper part 

 of Fig. 1 8 was probably formed in this way, though it is possible 

 that it is composed of more chromosomes. 



Fig. 1 8 represents a cell similar to that shown in Fig. 17. 

 These cells were found together with many other similar cells 

 in the same tubule, and several tubules bearing such type of 

 cells were observed. All of these cells were characterized by a 

 large clump of chromosomes, which was presumably an attempt 

 at plate formation, and a large number of chromosomes, uni-, 

 bi-, tri-, and even quadrivalent, are scattered about the entire 



