42 J. E. WODSEDALEK. 



PLATE V. 



50 and 51. Late anaphase of division in a secondary spermatocyte which re- 

 ceived the two accessories. Each of the latter divides in this stage. Figure 50 

 shows streaks of chromatin material uniting the two accessories. Usually no such 

 streaks occur (Fig. 51). 



52. One end of a late anaphase of a division in a secondary spermatocyte which 

 received the two accessories. The latter are oval in shape and smaller than the 

 bivalent autosomes. 



53. A spermatid which received the accessories, showing a common arrangement 

 of the chromosomes before they break up. 



54. Division of a secondary spermatocyte which apparently received the ac- 

 cessories. The chromosomes are so massed as to render a count impossible and 

 the two streaks which rarely occur are probably due to retarded division of the 

 accessories. 



55. An early spermatid in which the chromosomes have broken up, while the 

 two nucleoli remain in full evidence and are apparently the same thing as the 

 accessories. 



56. An early spermatid, which received the accessories, showing a characteristic 

 breaking up of the bivalent autosomes into univalents. Two of the autosomes had 

 divided almost completely while the other two also show signs of division. The 

 accessories are univalent in nature. 



57. A spermatid, which did not receive the accessories, showing a common ar- 

 rangement of the four bivalent chromosomes. Very frequently these autosomes 

 divide before they become massed together, as is the case of the autosomes in the 

 other type of spermatids represented in Fig. 56. 



58. A spermatid showing the reconstruction of the nuclear wall while the four 

 bivalent chromosomes are still in full evidence. 



59. Late prophase of a somatic cell, found in the mesonephros of a male pig 

 embryo, showing eighteen distinct rod-shaped and oval chromosomes two of which 

 are somewhat larger and are apparently the two accessories. 



60. Late prophase of an oogonial division showing twenty chromosomes, four 

 of which are longer and evidently the accessories. 



61 and 62. Somatic cells, found in the mesonephros of a female pig embryo. 

 Figure 61 shows a very uncommon condition revealing ten large chromosomes 

 which apparently resulted from the pairing of the twenty chromosomes. Two of 

 these are considerably larger and are interpreted as the result of the pairing of the 

 accessories. Figure 62 shows the late prophase of division in a type of somatic 

 cell occurring most frequently, and reveals a count of twenty chromosomes four 

 of which are considerably larger than the others. 



63. A full-grown Sertoli or nurse cell. 



