698 THK GENERATIVE ORGANS. 



\\'hcther they are active when first discharged from the male 

 I do not know. I formerly supposed this to be the case, 

 and that they find their way into the spermatic capsules by 

 their vibratile movements. I now think this extremely im- 

 probable. 



The spermatozoa removed from the testis often exhibit a 

 transparent disc-like organ at one extremity of the filament. 

 I formerly mistook this for the head and neck of the sperma- 

 tozoon ; it is usually regarded as the coiled extremity of the 

 filament. I am doubtful as to its true nature, and am rather 

 inclined to consider it as the result of a post-mortem change 

 produced by the imbibition of fluid, causing the neck to be- 

 come swollen into a thin-walled, flattened vesicle ; it certainly 

 resembles the stroma of a human red blood corpuscle after 

 the discharge of its colouring matter, by the addition of water 

 to the blood. 



The examination of the spermatozoa of this insect is at- 

 tended with technical difficulties, as it is exceedingly difficult 

 to obtain any of the sperm in an uncoagulated condition ; I 

 had intended to pay some attention to this subject last summer, 

 but as my time was fully occupied in other investigations I did 

 not do so, and I am therefore unable to give a more precise 

 description of the spermatozoa. 



e. The Development of the Ovaries and Ova in the Pupa and 



Young Imago. 



The development of the ovaries progresses very slowly in the 

 pupa stage. The pyriform ovary gradually becomes a disc 



I >l .>' KM'I ION (il Pl.ATK XI. IX. 



The development of the ovaries and ova of the Blow-fly. 



l-'n;. I. A section of the ovaiy of a Blow-fly pupa on the eighth day of the pupa 



stage, seen with a \ inch objective. <, epithelial cells developed from the neck 



of the ovary ; in, mesoblastic stroma ; p r, pseudo-yelk ; .r, cavity of the ovary ; 



/, tuliuli--. : _r, yolk -stocks. 

 I . 2. ^ lion through the ovary of a young female Blow-lly, seen with a J incli 



objective, ch, chorion of young egg ; e, young ova (yelks) ; ;;/, mesoblastic cells ; 

 ..\.irian follicles; o /, ovarian tubules; f<, peritoneal coat of the ovary; 



J/t egg-stalk ; /, terminal chainl er ; //-, tracheal vessels. 



