DEVELOPMENT OF THE GENERATIVE ORGANS. 703 
the more fully-formed ova may probably be destined in turn to 
be enclosed in a chorion, and to form an intervening ovum. 
It has also occurred to me that in many of the drawings this 
appearance is due to the section having been tangental to the 
egg-tube, so that a portion of the yelk mass appears outside 
the chorion. Many of Brandt’s drawings indicate that this 
may be the case. I am inclined to think that it is more prob- 
able that some such explanation may account for the appear- 
ances, than that there is such a wide difference in the manner 
in which the Merdistic ova are developed in different Insects, 
since there is certainly no question as to the multicellular 
origin of the ova in the Blow-fly. 
f. The Development of the Utero-Vaginal Tube and its Appendages, 
and of the Oviducts and Parovaria. 
It is now well established that the utero-vaginal tube and 
its appendages, the receptacula seminis, are developed in 
Insects from the hypodermis independently of the genital cord ; 
but the oviducts and their tube are believed to be developed 
from the genital cords, and to correspond, therefore, with the 
vasa efferentia and vas deferens of the male. 
Witlaczil [102] stated in general terms that the secondary 
ducts, my utero-vaginal tube, ejaculatory duct and sac 
originate in Aphides as involutions of the hypodermis; and 
Mayer [812], Bessels [824], and Ludwig [845], believed that 
the oviducts are developed independently of the ovaries. In 
1877 Huxley wrote : 
‘Nothing is certainly known respecting the origin of the 
vagina and oviducts, though it may be suspected that the 
posterior prolongations of the ovaries give rise to the latter.“* 
The first precise observations on the development of the 
secondary sexual ducts are due to Nussbaum. His paper is, 
unfortunately, in Polish; but his conclusions, as given by him- 
self [846], are to the following effect : 
(1) The current impression that the primitive ducts (sexual 
* © Anat. of Invertebrated Animals,’ Lond., 1877, p. 444. 
40 
