698 THE GENERATIVE ORGANS. 
Whether 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. beaks 
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 
DESCRIPTION OF PLATE XLIX. 
The development of the ovaries and ova of the Blow-fly. 
Fic. 1.—A section of the ovary of a Blow-fly pupa on the eighth day of the pupa 
stage, seen with a } inch objective. e, epithelial cells developed from the neck 
of the ovary ; 7, mesoblastic stroma ; / y, pseudo-yelk ; s, cavity of the ovary ; 
Z, tubules ; 7, yelk-stocks. 
Tic. 2.—Section through the ovary of a young female Blow-fly, seen with a } inch 
objective. c/, chorion of young egg ; e, young ova (yelks) ; #, mesoblastic cells ; 
of, ovarian follicles ; 0 ¢, ovarian tubules; /, peritoneal coat of the ovary; 
st, egg-stalk ; ¢, terminal chamber ; “7, tracheal vessels. 
