Sl^EEMAfOGENESlS OF STENOBOTHRUS VIJRIDULUS. 7 



be dissected out as a single body : they consist o£ a number o£ tubular 

 follicles, tapering at the ends, and opening posteriorly into a duct com- 

 municating with the vas deferens. 



By numbering the follicles in a section, and allotting the same numbers to 

 corresponding follicles in successive sections of a complete series, it is possible 

 to reconstruct the follicle in any particular case, and to recognize the true 

 position of one section in the whole, in cases where the razor has cut 

 transversely or at an angle to the plane of length. 



Primary^ Sperm - 



atoffonia . 



''*^« Secondary ditto. 



,2'''^' Growth period. 

 Pr/mary Sperm- 

 •v.^ arocytes. 



^^''=''/^'&2"f(maturation' 

 X, dtv/sions. 



,^^ '^^Spermat/ds • 

 '^'^' Unripe Sperm - 

 ' --^^ atozoa. 



"1\zBunct7es of'r/pe 

 '"'y Sperm arozoa . 



^. De^enerar/ny 

 "' Cet/s. 



At the anterior end of each follicle is a single cluster of primary spermato- 

 gonia with the apical cell, and several clusters of secondary spermatogonia, 

 arranged without definite order. The resting- or growth-^S'tages of the 

 primary spermatocytes occupy a considerable area, lying posteriorly to 

 the spermatogonia ; and the heterotropic chromosome is here seen for the 

 first time as a dark and compact body apposed to the nuclear membrane. 



We next see the various phases of the primary and secondary spermatocyte 

 mitoses, there being no resting-stage between these two divisions. Pro- 

 ceeding still further towards the posterior end of the follicle, we meet with 

 the transformation from spermatids to unripe spermatozoa ; the former are 



