.288 BALBIAXI^ ON SEXUAL 



A more or less narrow granular zone, the last traee of the 

 nuclear plasma, still, for some time, continues to separate 

 these bundles, but afterwards wholly disappears. Sometimes, 

 before vanishing, the granulations of this zone fuse together, 

 enlarge, assume an elongate, ovoid form, and range them- 

 selves in a regular series, placed transversely about the middle 

 of the cell. Each spermatic filament then appears to ter- 

 minate in a slightly swollen extremity, which represents the 

 head. This form, however, does not agree with the fully 

 matured condition of these elements, for by degrees, the head- 

 like swelling diminislies as it becomes more slender, and 

 finalty altogether disappears. ^^ 



" AVhen the male element has attained complete maturity 

 its form is that of an ovoid vesicle or capsule, extremely de- 

 licate, transparent, and pale. Its size is nearly the same as 

 that of the egg arrived at the term of its development. Ob- 

 served in the living animal, with the aid of gentle compres- 

 sion, it appears as a simple clear spot in the interior of the 

 body, and one recognises but very imperfectly the bundle of 

 iilaraents enclosed ia its interior, which only become per- 

 ceptible after treatment with acetic acid, iodine, or other 

 appropriate reagents. Under these conditions, a magnifying 

 power of from 200 to 300 times enables one to perceive the 

 fasciculate appearance of the capsule's contents ; but, in 

 order to make out the more delicate filaments of the sper- 

 matic tuft, it is necessary to have recourse to more powerful 

 magnifying powers, assisted by a favourable day, and an 

 obliqvie illumination obtained by means of a suitable inclina- 

 tion of the mirror. These filaments then appear uuder the 

 form of a straight bundle, stretched from one end of the 

 capsule to the other. Here and there they are grouped in 

 secondary tufts of greater or less size, and parallel to one 

 another. It is not impossible that this fasciculate arrange- 

 ment of the principal tuft may be an effect of retraction due 

 to the action of the reagent made use of. Whether this be 

 so or not, the form of these tufts allows us to gain a clearer 

 idea of that of the isolated spermatozoa, these last being 

 often difficult to recognise by reason of their extreme delicacy 

 and transparency. Tiiey are minute hair-like bodies, 

 straight, somewhat rigid, of extreme tenuity, very slightly 

 swollen towards the middle, and terminated at each end by 

 an attenuated point, which cannot be traced through its 

 entire extent. Consequently they do not offer a distinct 

 head and tail, as in many other animals ; and it is with the 

 spermatic filaments of the Turbellaria and several Mollusca, 

 that they have the greatest resemblance." 



