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 Meroistic 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 TTtero-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 tubae 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 [312], Bessels [324], and Ludwig [345], 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 Nussbaurn. His paper is, 

 unfortunately, in Polish ; but his conclusions, as given by him- 

 self [346], are to the following effect : 



(i) The current impression that the primitive ducts (sexual 

 * ' Anat. of Invertehrated Animals,' Lond., 1877, p. 444. 



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