THE SPERMATOGENESIS OF AGALENA N/F.VIA. 13! 



dimorphism of the spermatozoa is not concealed, for in half of 

 them can be seen a slender, darkly stained band extending along 

 the middle of the convex surface of the head, from the anterior 

 to the posterior end, although it fades out often near the hinder 

 extremity. This chromatic band represents the fused and some- 

 what modified accessory chromosomes whose distribution to but 

 one half of the spermatozoa divides them into two distinct groups 

 (Figs. 53 and 54). 



In the mature spermatozoon the distal centrosome is no more 

 in evidence, the axial filament has increased in length and its 

 vesicles have disappeared. Whether or not the vesicles con- 

 tribute their substance to the axial filament as it grows in length 

 and whether or not the latter is supplied with a cytoplasmic in- 

 vestment, I am unable to say. The proximal centrosome forms 

 a slight projection on the lower side of the head and probably 

 corresponds to the end-knob of other forms. Wagner described 

 it as a " little tooth " which lies at the point where the axial fila- 

 ment joins the chromatin plate and Bosenberg regards it as the 

 middle piece, or rather as the " connecting piece," the former 

 term not being applicable in the case of the spider spermatozoon. 

 At the anterior end of the head is a transparent, apparently 

 cylindrical body which in Lycosa, according to Bosenberg, is 

 derived from the idiozome vesicle. Forming an axis in this apical 

 body is a distinct fiber or filament which projects beyond the 

 apical body and bears a deeply staining granule at its extremity. 

 I cannot state positively the origin of the apical granule or of the 

 filament which bears it but in some preparations, after long ex- 

 traction, there is seen what appears to be a delicate filament 

 passing from the end-knob, through the anterior portion of the 

 head, and becoming continuous with the filament in the apical 

 body. The distinctness of the filament within the head is exag- 

 gerated in the figures. 



The spermatozoon now works itself free from the cell-body, 

 the anterior end of the head protruding first. The escape is 

 probably effected by the contractions of the head itself. Even 

 after the posterior end of the head has entirely lost its connection 

 with the cell-body, the spermatozoon is not yet ready to pass into 

 the lumen of the testis (Fig. 55). First there occurs a very 



