EXPL NATION OF PLATE XXIV & 1^1.^ -continued. 



Fig. 29.— Copied from v. la Valette St. George, shows a later stage of 

 the above. 



Tig. 30 is a stage from the same source, which corresponds to Fig. 28 

 of Meyer's. 



Fig. 31. — Copied from Meyer, shows the spermatocyte, which is to be 

 known by its|granular appearance in connection with the Spermatogone, to 

 which it owes its origin. 



PLATE XXV. 



All the figures relate to the Common Frog. 



Fig. 1. — Transverse section across a testicular crypt of the frog, about 

 the end of the summer. Next the wall (?<7.) of the crypt is the testicular 

 epithelium (t. e.), composed of two kinds of cells, one the spermatospores 

 («)., destined for future crops of spermatozoa, the other interstitial support- 

 ing cells (i. c.) i n., nuclei of fibres forming the wall of the crypt. Next 

 the epithelium are bundles of spermatoza {b. s.), arranged radially with 

 their tails towards the lumen and their heads towards the periphery sup* 

 ported on the blastophors. 



Figs. 2 — 8. — Bundles of spermatozoa from a testis in the same stage as 

 Fig. 1, shows the spermatozoa united by their elongated heads to a blasto- 

 phoral cell {b. c). 



Figs. 9 — 21. — Sta^jes in degeneration of blastophoral cells, the nuclei 

 appear to have been broken up into small pieces, and the protoplasm to 

 have become vacuolated. 



Fig. 22. — Transverse section of a crypt about the end of July, showing 

 the large swollen polyplasts {s. p.) in various stages of growth ; other 

 letters same as Fig. 1. 



Fig. 23. — A polyplast stained with picrocarmine, it shows the super* 

 ficial nuclei (s. n.) each surrounded with a portion of granular plasma. 



Fig. 24. — Ditto, after longer staining. 



Figs. 25 and 26. — Polyplasts stained in a solution of magenta. The 

 staining fluid reaches and stains the superficial nuclei («. «.) before it can 

 act on the spermatoblasts. 



Figs. 27 — 29. — Polyplasts from sections showing a difference in the 

 appearance of the nuclei, due to a difference in the arrangement of the 

 nuclear network. 



Fig. 30. — A polyplast viewed in the fresh state, it shows the superficial 

 nuclei {s. n.). 



Fig. 31. — Transverse section of a crypt about the middle of August. 

 It shows the vesicular polyplasts (*. p.) breaking up, and the spermatoblasts 

 coming into connection with one of the superficial nuclei, as at a ; then 

 falling back with it, as at b, on to the wall of the crypt, and finally assum- 

 ing a radial position with regard to the wall of the testicular crypt. 



Fig. 32. — Surface view of a vesicular polyplast. 



Fig. 33. — Optical section of a polyplast. 



Figs. 34 — 37. — Polyplasts from sections which show the centripetal 

 elongation of the plasma of the spermatoblasts to form the tail of the 

 mature spermatozoa, s. n., superficial nuclei, in 37 the spermatoblasts may 

 be seen coming into connection with these bodies. 



Fig. 38. — Spermatoblasts arranged round one of these superficial nuclei, 

 which has now become the blastophoral cell. 



Fig. 39. — Interstitial cells from young testis. 



