444 Sidney I. Koriihauser 



Explanation of Plates. 



All figui'es are of Hersilia apodijormis and were made with the aid of a cainera 

 lucida. The figiires of Plate I were made at a magnification of 850 diameters and not 

 reduced: Zeiss apochromatic objective 1,6 mm, compensating ociüar No. 2, projec- 

 tion distance 295 mm. In the figiires of Plates II — III. with the exception of figure 53, 

 the combination used was Zeiss apochromatic objective 1,5 mm and compensating 

 ociüar No. 12, the projection distance 440 mm. Magnification 3500 diameters sub- 

 sequently reduced Vs- 



Abbreviations. 



Vqt. = bouquet stage; r. = ring-form pair of chi'omosomes ; 



cg. = conjugating pair; s. = single chromosome \\'ithout "Quer- 



cpl. = cytoplasmasomes; kerbe"; 



h. = heterochromosome; 2nd mal. = second niatiu'ation division; 



kp. = Keimpolster; sp'g = spermatogonia; 



n.c. = nuclear cap; sp't = spermatid; 



nll. = nucleolus; sp'z = spermatozoa; 



o'ct. = oöcyte; ug. = primordial germ cell. 



Plate IV. 



Fig. 1. Longitudinal section of testis and "Keimpolster". a — g, region corre- 

 sponding to that shown in Plate X, Fig. 12. 



Fig. 2. Longitudinal section of ovary of immature female such as represented 

 in textfigure C. page 405. 



Fig. 3. Longitudinal section of portion of matiu-e ovary, extending from the 

 bend to the uterine processes. 



Fig. 4. Longitudinal section of hermaphroditic sex-gland and "Keimpolster''. 



Plate V. 

 Figs. 5 — 11. Spermatogonia. 

 Fig. 5. Quiescent spermatogonium, 

 Figs. 6 — 7. Projibases of spermatogonial mitoses. 

 Fig. 8. Metaphase equatorial plate, spermatogonium. 

 Fig. 9. Anaphase spermatogonial division. 



Fig. 10. Telophase spermatogonial division, showing only one of the sister cells. 

 Fig. 11. Reconstruction of nucleus after spermatogonial division. Only one 

 of the sister cells figiu^ed. 



Figs, 12 — 28. Spermatocytes. 



Fig. 12. Stages in the growth period of the spermatocytes. a — c, formation of 

 leptotene threads; d, early leptotene; e, leptotene bouquet; /, /', conjugation stages; 

 g, zygotene bouquet stage. 



Fig. 13. Optical section of leptotene stage viewed from positive pole. 



Figs. 14 and 15. CeUs showing the conjugation of leptotene threads. 



Fig. 16. Optical section of cell, showing conjugation, viewed from positive pole. 



Fig. 17. Zygotene bouquet stage in lateral view. 



Fig. 18. Optical section of zygotene bouquet stage, polar view. 



Figs. 19 — 21. Strepsistene stage showing various methods of Separation of the 

 conjugants. 



