DEVELOPMENT OF THE OVARIES IN THE BLOWFLY. 



433 



stand how this duct has been overlooked, or how it has been 

 supposed that the glands open into or with the seminiferous 

 capsules. The gum-glands have also probably been confounded 

 with true vaginal glands, which appear to exist in some insects. 



I shall again refer to the guin-glands in a special sectiou of 

 the present paper in relation to their structure and functions. 



The uterus (figs. 1, 2, 3, ut.) is a tbick-walled sac lined by a 

 strong cuticular membrane, very diflferent to the thin cuticular 

 membrane lining the oviduct. It bas a diverticulum or pouch 

 {p) on its dorsal wall immediately behind the orifice of the 

 common oviduct. This pouch (sacculus, figs. 1, 2, and 3, p) 

 is lined by a very thick lamiuated cuticle with a projecting 

 median ridge which appears to divide it into two lateral pockets. 

 Each of these pockets opens behind into the uterus, and is 

 usually filled with a clear colloid mass, which stains very deeply 

 with alkaline carmine. It has all the appearance of being the 

 same material as that which cements the eggs together when 

 they have been deposited. The same contraction of the uterus 

 which expels the egg would certainly expel some of this material 

 from the uterine pouch. 



4. The Structure of tJie Gum-glands. 



Although I have used the term gum-glands to designate 

 these organs, it will be seen that there is nothing in their 

 structure to justify its use. And although they are usually 

 regarded as secretin g-glands which form a glue or cement for 

 the attachment of the eggs, a function first apparently ascribed 

 to them by Burmeister (7) and afterwards by Loew (18), Stein, 

 who has examined these structures with more care perhaps than 

 any other writer, entirely discards the view. He regards the 

 so-called gum -glands as accessory organs of fertilization except 

 in the Hydrophilida), where they open into the calyx of the 

 ovary ; and, curiously enough, disregarding the extreme impro- 

 bability that gum-glands would open in such a situation, makes 

 an exception in these insects, and regards the glands as gum- 

 glands. Stein further identifies these glands in the Diptera 

 with his " glandular portion of the organs of fertilization." 



