EXPLANATION OF PLATE XXIII. 



Drawings made from sections of the testis of Phrynotettix magnus. 



Fig. 1. — Metaphase of a spermatogonia! cell showing all of the chromo- 

 somes, (x) Accessory chromosome. 



Fig. 2. — Typical spermatogonia! cell in anaphase, (x) Accessory chro- 

 mosome. 



Fig. 3. — Telophase of the same showing the persisting spindle fibers. 



Fig. 4. — Later telophase. Note the encroaching division-wall contracting 

 the spindle. The section is cut parallel with the long axis of the 

 chromosomal vesicles, (x) Accessory chromosome in longitudinal sec- 

 tion, (a) Polar granule. 



Fig. 5. — Cross- section of the chromosome group of a cell in the same stage 

 as those shown in figure 4. The polar granule of the accessory is 

 shown. 



Fig. 6. — A telophase slightly later than that shown in figures 4 and 5. 

 Polar granules located at the proximal ends of the chromosomes. 



Fig. 7. — Cross-section through the proximal end of a group of chromo- 

 somes showing a number of polar granules. 



Fig. 8. — A cross-section through the distal portion of a similar group. 

 No chi'omatin bodies of definite form appear in this plane. 



Fig. 9. — A typical spermatogonia! cell showing the diffusion of chromatin 

 at its maximum within the vesicles. This stage marks the end of the 

 telophase. 



Figs. 10, 11, 12, 13, 14, 15. — Cells showing the succession of typical 

 changes occurring in the spermatogonia! prophases, (x) Accessory 

 chromosome. 



Fig. 16. — Early spermatocyte prophase. (rr) Accessory chromosome 

 showing its characteristic position. The lesser bodies are the polar 

 granules. Note the looped arrangement of the chromatin thread. 



Fig. 17. — A slightly later spermatocyte prophase. The chromatin thread 

 is conti-acting. (x) Accessory chromosome. 



Fig. 18. — Spermatocyte tetrads. The bulbous thickening or polar gran- 

 ules mark the point of spindle fiber attachment, a, e, h, show the 

 tetrads which later form the large rings shown in figures 22 and 23. 

 (/) is a similar tetrad in a more condensed state. In (h) the sepa- 

 ration resulting in bivalent chromosomes has begun. In (6) the 

 separation has apparently progressed still further. 



Figs. 19, 20. — The same stage as shown in figure 17. (x) Accessory 

 chromosome with no chromatin threads attached, (a) A deeply stain- 

 ing mass of homogeneous chromatin with radiating chromatin threads 

 showing a longitudinal division. The chromomeres are in evidence. 



