STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 471 
Fig. 12. — Experiment No. 8. Section through testis. X 21. 
bl. Blood-vessels. 
Fig. 13. — Experiment No. 9. Section through testis. X 21. 
Fig. 14. — Experiment No. 10. Section through testis No. 1. x 21. 
bl. sp. Large blood-spaces, occupying more than half the area of the 
section, tub.dg. Degenerating tubules, tub. rg. Regenerating tubules. 
Fig. 15. — Experiment No. 10. Section through testis No. 2. x 21. 
fib. Central mass of fibrous tissue, tub. rg. Tubules lined with living 
and proliferating spermatogonia. 
Fig. 16. — Experiment No. 10. Part of testis No. 1. X 199. Showing 
blood-spaces (bl. sp.), degenerating (tub. dg.) and regenerating tubules 
(tub. rg.). 
Fig. 17. — Experiment No. 10. Small regenerating tubule from testis 
No. 1. x 545. 
Fig. 18. — Experiment No. 10. Part of central fibrous portion of 
testis No. 2. x 545. 
PLATE 45. 
Fig. 19. — Experiment No. 10. Testis No. 2. Tubule from the end of 
testis lined with actively proliferating cells, x 545. 
Fig. 20. — Experiment No. 11. Testis No. 1. X 21. fib v Fibrous 
surrounding layer containing large quantity of pigment (pi.), fib.,. 
Central fibrous portion, tub. Regenerating tubules. 
Fig. 21. —Experiment No. 11. Testis No. 1. A portion from near 
the periphery. X 250. Lettering as above. 
Fig. 22. — Experiment No. 11. Testis No. 2. x 21. bl. Blood- 
vessel. tub. reg. Regenerating tubules, tub. dg. Degenerating tubules. 
PLATE 46. 
Sections of thumb-pads. X 67. 
ep. Epidermis, gl. Glands, pi. Pigment. 
Fig. 23. — Experiment No. 14. 
Fig. 24. — Experiment No. 15. 
F'ig. 25. — Experiment No. 16. 
Fig. 26. — Experiment No. 11. 
Fig. 27. — Experiment No. 17. 
Fig. 28. — Experiment No. 18 on October 20th, 1910. 
Fig. 29. — Experiment No. 18 on November 6th, 1910. 
Fig. 30. — Experiment No. 19 on October 20th, 1910. 
Fig. 31. — Experiment No. 19 on November 16th, 1910. 
Fig. 32 . — Normal frog (l.) killed in August. 
