704 THE GENERATIVE ORGANS. 



cords) unite and give origin to the whole system of sexual 

 ducts is incorrect : they only form the vasa deferentia (my 

 vasa efferentia) or the oviducts. 



(2) All the other parts of the efferent canal are developed 

 from the hypodermis. 



(3) The connective tissue and muscaluture are derived from 

 the mesoblast. 



(4) The efferent ducts originate as paired rudiments ; all the 

 azygos parts of the efferent apparatus are at first paired. The 

 azygos efferent apparatus of Insects must, therefore, be re- 

 garded as morphologically a secondary and more complicated 

 form. 



(5) The male and female efferent ducts are strictly homolo- 

 gous. 



(6) The cavities of the oviducts arise independently, and 

 come into relation secondarily with the primitive ducts of the 

 gonads, which are developed from the solid genital cord. 



Hatchett Jackson [351], in an important memoir on the 

 development of the oviducts and accessory sexual apparatus in 

 Vanessa lo, has shown conclusively, I think, that the bursa, 

 vagina and azygos oviduct of this insect are developed from 

 the hypodermis, which are at first paired pouches, imaginal 

 discs. These pouches unite and form an open groove on the 

 ventral surface of the pupa from which the bursa and azygos 

 oviduct are subsequently developed. The author has not 

 apparently investigated the manner in which the paired ovi- 

 ducts arise, but assumes that they are formed from the genital 

 cords. 



The Genital Cord in the Blow-fly undoubtedly becomes con- 

 verted into a hollow epithelial tube surrounded by a peritoneal 

 investment of extreme tenuity at a very early period in the 

 development of the pupa. On the sixth or seventh day of the 

 pupa stage, I have succeeded in dissecting out the whole of 

 the genital ducts and ovaries. A drawing of the preparations 

 is given in Fig. 101. It will be seen that the genital cords 

 have indubitably become the tubular parovaria. The anterior 

 ends of these organs are closed, and are imbedded in the 



