PLATE LXX. 



These photomicrographs were made with a Zeiss 2mm., 1.40 N. A. 

 apochromatie objective and No. 4 projection ocular, the camera bellows 

 being extended so as to place the sensitive plate at a distance of thirty- 

 one inches above the object. Illumination was furnished by Welsbach 

 mantle, the light passing through a Watson Parachromatic oil immersion 

 condenser with the diaphragm set at N. A. 1.0. The original magnification 

 is 1500 diameters which, in reproduction, has been reduced to 1000 

 diameters. Considerable detail has been lost in reproduction, especially 

 in figui-es 3, 7 and 8. 



Fig. 1. — Polar view of spermatogonial metaphase, showing 21 chro- 

 mosomes. 



Fig. 2. — Same as figure 1. 



Fig. 3. — Same as figure 1. 



Fig. 4. — First spermatocyte prophase, in which the accessory chromo- 

 some is bent in the middle. This is the nearest approach to the spireme 

 condition found in Anasa. 



Fig. 5. — Later prophase with the accessory extended and showing the 

 longitudinal split. 



Fig. 6. — Same stage as in figure 5. 



Fig. 7. — -A portion of three cysts appears in this photograph. In the 

 lower one the last generations of spermatogonial chromosomes are seen 

 in several cells. At the upper right-hand corner are four cells in 

 synizesis. 



Fig. 8. — Parts of three cysts are included in this picture. The cells in 

 each are in some stage of synizesis. The presence of the accessory chro- 

 mosome on the periphery of the nucleus and of the plasmasome in the 

 synizetic knot is demonstrated in several cells. The stages shown in 

 figures 7 and 8 precede the ones represented in figures 4, 5 and 6. 



Fig. 9.— Post-synizetic stage, in which the peripheral accessory and the 

 more central plasmasome are shown in several cells. This may be com- 

 pared with a similar condition in cells prepared according to the method 

 of Foot and Strobell, as shown in their figures 11 and 12, in order to 

 judge of the correctness of their belief that the smear method preserves 

 delicate detail better than sections. It may be pointed out also that there 

 is little liability to confuse either of the nucleolar bodies with karyosomes 

 resulting from concentrations of the chromatin elsewhere. Wilson's slide 

 9496. Photos 1 to 9 from sections. 



Fig. 10. — Chromosomes of the first spermatocyte metaphase, smear 

 preparation. The lowermost chromosome is the accessory. It is seen to 

 have one plane of division, while the others have more or less distinct 

 second planes indicated. In this cell the five lower chromosomes have 

 dried thinner and spread more than the upper six and show wrinkles and 

 other distortions. Wilson's Woods Hole "x" slide. 



Figs. 11-15. — Photographs from sections on Wilson's slide 9496, show- 

 ing the accessory chromosome and plasmasome in the first spermatocyte 

 prophase at about the same stage as that of figure 9. It is difficult to 



