PLATE 1 
EXPLANATION OF THE FIGURES 
1 Transverse section of a testicular tubule of a small crab, fixed in Petrunke- 
witsch’s fluid; spermatogonia at the top; spermatozoa at the bottom, spermatids 
between. X 450. 
2 Transverse section of testicular tubule, p.s., primary spermatogonial cell. 
The mass of spermatogonia larger than in figure 1. X 450. 
3 Transverse section of testicular tubule, showing larger mass of sperma- 
togonia; p.s., primary spermatogonial cell. > 450. 
4 Transverse section of testicular tubule, showing a large mass of sperma- 
tocytes in synapsis; p.s., primary spermatogonial cell. » 450. 
5% Resting phase of a spermatogonial nucleus. 
6 Prophase of a spermatogonial nucleus showing the paired chromosomes 
which were seen in the upper one-half of the nucleus. 
7 Optical section of a spermatogonial nucleus showing the peripheral arrange- 
ment of the paired chromosomes in the prophase. 
8 The miotic figure in a spermatogonial division. 
9% Harly prophase of the first miotic division of the spermatocyte. 
10 Synapsis in the first miotic division of a spermatocyte. 
11 to 12 The stage following synapsis, showing the spireme loosened up and 
separating into chromosomes. 
13 First miotie division; stage just preceding the formation of the equatorial 
plate. 
. 14 Equatorial plate and spindle in first miotic division. 
15 A tripolar division of the nucleus of a spermatocyte of the first order. 
Figure 15a is a drawing of the same nucleus made from a lower plane and show- 
ing a portion, e, of the chromatin which was not included in the equatorial plate. 
16 Chromosomes found in the equatorial plate of the first miotic division. 
16aandb Portions of the first miotic figure in the metaphase, showing the 
chromosomes. 
2 Figures 5 to 112 (except 70 to 72) were all drawn with the camera lucidia and 
a Zeiss 1.5 mm. apochromatic objective and a compensating ocular (either a No. 
6 or No. 8). Then the drawings were enlarged so that in the plates there is a 
magnification of 3000 diameters. In making figures 70 to 72 the camera lucida 
was not used. 
* Figures 9 to 58 were copied by Mr. E. A. Morrison. 
183 
