2l8 N. M. Stevens 



Description of Figures 



The figures were all drawn with camera lucida. Fig. 5 was drawn with Zeiss 16 mm. compens. 

 4; all others figures with Zeiss 1.5 mm, compens. oc. 12. The plates were reduced one-fourth. 



Fig. I Oogonium showing 3 pairs of chromosomes in equatorial plate. Ac-c-prep. 



Fig. 2 Three pairs of chromosomes from another oogonium. Ac-c. 



Fig. 3 Chromosomes and plasmosome(/))from a youngoocyte. Ac-c. 



Fig. 4 Nucleus of an older oocyte showing 3 separate spireme threads. Ac-c. 



Fig. 5 Outline camera drawing of a testis mounted in aceto-carmine and flattened by pressure on 

 the cover-glass, a = cyst of resting spermatogonia; h = spermatogonia in anaphases and telophases; 

 c,d,e ^ synizesis stages; / = second spermatocytes in stage seen in Fig. 44; g, h, i, j — spermatids; k — 

 masses of spermatozoa. Ac-c. 



Fig. 6 Spermatogonium from tip of testis, early prophase showing one chromatin thread sepa- 

 rating into its component chromosomes \z-z. 



Fig. 7 Section of a nucleus of a spermatogonium showing twisted pairs of chromosomes in prophase 

 of mitosis. 



Fig. 8 Spermatogonium showing three pairs of chromosomes in metaphase Ac-c. 



Fig. 9 Chromosomes from another spermatogonium in outline. Ac-c. 



Fig. 10 Section of a spermatogonium showing all three pairs of chromosomes in late prophase. 



Fig. II Chromosomes from one of 7 equatorial plates found in spermatogonial cysts in two indi- 

 viduals. The smaller pair of chromosomes appears to be composed of an equal and an unequal pair 

 combined. Ac-c. 



Fig. 12. Early synizeses stage from material fixed in Flemming and stained in thionin Plasmosome 

 (/>) pale yellowish. Sec. 



Fig. 13 Later synizesis stage from same section, plasmosome (/>) blue 



Fig. 14 Spireme growth stage from same section, plasmosome deep blue. 



Fig. 15 Late growth stage of first spermatocyte, focusing from the surface of the nucleus down to 

 the plasmosome (/>), and showing one end of a spireme double. Ac-c. 



Fig. 16 Prophase of a first spermatocyte mitosis showing the three twisted pairs of chromosomes. 

 Ac-c. 



