NEMIC SPERMATOGENESIS 



With a suggested discussion of simple organisms, Litobionts 

 CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY XVI 



BY N. A. COBB 



Definitions. Spermatidium: one of a plurality of cells derived 

 from a spermatid by subdivision; a secondary, tertiary, or quaternary, 

 etc., spermatid. Spermule: an individual 

 spermatidium which, after growth and 

 transformation, is capable of activating 

 or fertilizing an egg, being not a meta- 

 morphosed spermatid, but a descendant 

 of a spermatid, one or more cell-genera- 

 tions removed. 



The definitions will be better under- 

 stood by at once consulting the illustra- 

 tions, especially spmtd and spml Figs. 2 

 and 12. 



Spermatogenesis. At the blind end of 

 the single testis of the nema, Spirina para- 

 sitifera (Bastian '65) Filipjev (Figs. 1 

 and 2) , a free living marine species, com- 

 mon an inch or two deep in sand and 

 among small stones between the tide 

 marks of protected coasts on both sides 

 of the North Atlantic through a wide 

 range of latitude, the primordial gonic 

 elements give rise by 14-chromosome 

 mitotic division to numerous twin cells 

 (Figs. 2, 14), which arrange themselves 

 tandem in the testis (Fig. 3) where each 



dgng. 



Fig. 1. Lateral view of the 

 head of Spirina parasitifera. 

 The amphidial nerve, nrv amph, 

 expands into a sensilla, then 

 again into a 10-12 celled ganglion 

 (seen through the lateral chord, 

 chrd. lat.) joining the nerve-ring, 

 cor nrv. 



Waverly Press, Baltimore, Md., June 9, 1928. 

 material alterations. 



From Jour. Wash. Acad. Sc., Jan. 



Repaged without 



