32() 



J. E. niiOM FIELD. 



/-I 





\ 



/HMq/o 



O- O.OYO' 



Fig. 1. — Spermatogenesis of Selacliians. a. Transverse section of a very 

 young testicular ampulla of Scyllium. o. male ovules of Hermann (si)er- 

 niatospores, Blomfield). i. Prismatic cells with nuclei in course of 

 division, tn, n. Small cells resulting from division of the prismatic cells. 

 B. Portion of a similar transverse section at a later stage, o. Nuclei of 

 the male ovules now constituting multi-nucleate polyplasts and increased 

 in number by division of the prismatic cells, m. Terminal nuclei bounding 

 the lumen of the ampulla, c. Similar piece at a later stage, o. The 

 nuclei no longer arranged in rows. n. The basilar nucleus of Semper 

 (blastophoral cell of Blomficld). d. Section showing two sperm-polyplasts 

 or mother-cells longitudinally cut at a stage immediately preceding the 

 conversion of the spermatoblasts (/) into spermafozoa. ;;. Axial proto 

 plasm of the polyplast. c. Basilar portion of the polyplast. n. Basilar 

 nucleus (f and n form the blastophoral cell), e. Transverse section o 

 similar cells, m , in. Intercalary processes of the protoplasm of the poly 

 plast. V to L. Conversion of a spermatoblast (final stage of division o 

 the nucleus and protoplasm of an original mother cell) into a spermatozoon 

 ?^. Nucleus. ?/." Corpuscle |)rccurseur." o. Cephalic nodule. ;//. Middle 

 piece. ./. Flagellum. 



