Journal of microscopical science. 



EXPLANATION OF PLATES XXIV & XXV, 

 Illustrating Mr. Blomfield^s Paper on '' Spermatozoa/ 



Figs, 1 — 23. — Helix. Figs. 24 — 31. — Various animals* 



Figs. I — 4. — Original cells which are destined to form the spermatozoa, 

 called on this account spermatospores, the spermatocytes of Meyer and 

 V. la Valette St. George. An intranuclear network is conspicuous in the 

 majority. 



biGs. 5 — 8. — Commencement of the process of spermatogenesis by mul- 

 tiplication and division of the nucleus with a corresponding constriction of 

 surrounding plasma. 



Figs. 9—12. — Various stages in the formation of the sperm -polyplasts. 

 These are multinuclear masses of a mulberry-like appearance, each nucleus 

 of which is surrounded by its own plasma and thus constitutes a sperma- 

 toblast. The whole mass of the spermatoblasts are supported on a darkly- 

 granular plasma, which possesses a large darkly-stained nucleus. This is 

 the blastophoral cell, or, more shortly, blastophor {b. c). 



Fig. 13. — Longitudinal optical section of a polyblast. 



Figs. 14 — 16. — Polyplasts, whose spermatoblasts are commencing their 

 transformations into spermatozoa. This consists in the nucleus becoming 

 placed at one pole, while the plasma elongates and draws away from itj 

 previously throwing out a filament forming the tail. 



Figs. IBaj — 18. — Isolated spermatoblasts with filaments. 



Figs. 19 — 22. — Elongation of the protoplasm to form the tail. The 

 plasma, being viscid, appears to elongate like a drop of viscid liquid, pre- 

 senting as it does so many thickenings and bead-like swellings, which often 

 gives the young tail a monilliform appearance. 



Fig. 23. — A bundle of nearly mature spermatozoa, united by their heads 

 to a blastophoral cell {b. c). 



Fig. 24. — A series of drawings from the spermatoblast to the mature 

 spermatozoon of the frog. 



Fig. 25. — A bundle of spermatozoa from the testis of Dytiscus. Super- 

 ficial to the bundle are seen several nuclei {s. n.), with surrounding plasma. 

 These seem, at first sight, similar to the superficial nuclei of the polyplast 

 of the frog. 



Figs. 26 and 27. — Bundles of spermatozoa from Pieris in different stages, 

 with the superficial nuclei (s. n.). 



Fig. 28. — Copied from Meyer's drawings. Sg. is his Spermatogone, and 

 Sge. is the Spermatogemme. It is obvious from the drawing that the two 

 correspond witii the polyplast of the snail and its blastophoral cell, though 

 according to his view the upper portion of the Spermatogemme is the result 

 of the nuclear multiplication of a separate cell, the spermatocyte, which is 

 derived from the Spermatogone at an early stage and shown in connection 

 with it in Fig. 31. 



