518 
Max Morse 
Explanation of Plates. 
All drawings were made by camera lucida with number 12 compensating 
ocnlar, (Leitz), and 2 mm apochromatic objective, (Leitz). They have not been • 
rednced in reproduction, Figs. 1 — 54, Pcriplaneta. Figs. 55 — 62, Leucophaea. 
Plate XXVI. 
Fig. 1. Primary spennatogonium. with 33 chromosomes. Metaphase. 
Fig. 2. Early interkinesis between primary and secondary spermatogonia 
The dark spherical body is chromatic, the remainder achromatic. 
Fig. 3. Later stage than 2 showing the beginning of chromosome formation. 
The chromatic body has assnmed a dumb-bell shape. 
Fig. 4. Secondary spermatogonium with 33 dumb-bell shaped chromosomes. 
Metaphase. 
Fig. 5. Metaphase of ovarian follicle cell, containing 34 rod or "U” shaped 
chromosomes. 
Fig. 6. Late anaphase of secondary spermatogonium. A plasmosome ap- 
pears near the Zwischenkörper. 
Fig. 7. Beginning of the primary spermatocyte stages. This stage follows 
directly on the secondary spermatogonial telophase. The plasmosome of the 
last spermatogonial division is shown out in the cytoplasm, while a new one is 
forming within the nucleus. The odd chromosome appears for the first time 
near the plasmosome as a larger sphere. 
Fig. 8. Stage following 7. The odd chromosome stains less deeply. 
Fig. 9. Assumption of the characteristic pear shape by the odd chromo- 
some. The plasmosome is applied closely to the blunter end of the odd 
chromosome. 
Fig. 10. The contraction stage of the growth period. 
Fig. 11. Polarization of the chromatic threads. The odd chromosome 
bears the spherical plasmosome at its blunter end. 
Fig. 12. Optical section of 11. The odd chromosome is seen to be split 
Fig. 13. Beginning of synapsis, immediately preceding 14. 
Fig. 14. Some of the threads show decided thickenings. The odd chro- 
mosome and the plasmosome are ragged in outline. 
Fig. 15. Optical section of 14. 
Fig. 16. Nearly all of the threads have becoine thickened. 
Fig. 17. Thickening affecting all of the chromatin loops. 
Fig. 18. Optical section of 17, showing, approximately, 32 points. 
Fig. 19. Chromatin loops at the close of the synapsis period. 
Fig. 20. The loosening up of the chromatin loops preparatory to forming 
the second polarization stage. 
Fig. 21. The second polarization stage. 
Fig. 22. Migration of one of the centrosomes, carrying with it some of 
the chromosomes. 
Fig. 23. Completion of the migration. The odd chromosome with the 
spherical plasmosome applied to it liev at the lower pole. 
Fig. 24. Formation of chromosomes as loops lease the poles. 
Fig. 25. The odd chromosome lies as the pear shaped body nearly in the 
center of the nucleus no longer attached to other chromosomes. Prophase. 
