38 J. E. WODSEDALEK. 



chromosomes to cooperate in functioning. Each group seems to 

 go on performing its functions normally. The real conflict 

 ensues during the various stages of the primary spermatocyte, 

 and is no doubt occasioned by the necessity for cooperation on 

 the part of the paternal and maternal chromosomes in the process 

 of conjugation or pseudo-reduction. 



14. Abnormalities in mitosis occur invariably in primary 

 spermatocytes that attain the metaphase stage. 



15. Giant cells are occasionally seen. 



1 6. The chromatoid body which is very conspicuous and 

 constant in the horse is entirely lacking in the mule. 



17. There is considerable evidence that primary spermatocytes 

 make an attempt to eliminate some of the chromatin material. 



1 8. The chromosomes expelled by the cells appear to be those 

 which were contributed by the mother of the hybrid. 



19. Destruction as well as abnormalities in mitosis seem to be 

 restricted to the primary spermatocytes. Most of the cells 

 disintegrate during the prophase, especially during the period of 

 synapsis. Others meet their fate in the metaphase or early ana- 

 phase stages. The remaining few that survive the anaphase 

 succumb soon after, and no secondary spermatocytes nor sper- 

 matids, and consequently no spermatozoa are formed and the 

 hybrid remains sterile. 



20. There are no authentic cases on record showing that fer- 

 tility ever occurs in this hybrid. 



LITERATURE CITED. 

 Galeotti, G. 



'93 Ueber Experimentelle Erzengung von Unregelmassigkeiten des karyokine- 

 tischen Processes. Beitr. z. patholog. Anat. u. z. Allg. Pathol., XIV., 2, 

 Jena, Fischer, 1893. 

 Guyer, M. F. 



'oo Spermatogenesis of Normal and of Hybrid Pigeons. University of Cin- 

 cinnati Bulletin No. 22. 



'10 Accessory Chromosomes in Man. BIOL. BULL., Vol. XIX., No. 4. 

 Hansemann, D. 



'91 Karyokinese und Cellularpathologie. Berl. Kin. Wochenschrift, No. 42 



1891. 

 Hayes, M. H. 



'04 Points of the Horse. New York. 

 Lustig and Galeotti, G. 



'93 Cytologische Studien ueber pathologische menschliche Gewebe. Beitr. 

 Path. Anat., XIV., 1893. 



