148 A. RICHARDS. 



outward and inward. The outward extension becomes the 

 vagina, seminal receptacle and fertilization canal; the inner not 

 only gives rise to the ovary and vitellarium but also to the re- 

 maining part of the oviduct, the vitello duct and the uterus. 

 These various structures are in no sense an invagination from 

 the outside for their development begins in the middle part of 

 their length and the connection with the outside, through the 

 cirrus pouch, is quite secondary to the formation of the lumen 

 of the tube. The lining is, of course, an epithelium; but it is 

 not an invagination from the exterior. That of the cirrus 

 pouch, however, is an invagination and might be looked upon 

 as an ectoderm. But in the other parts of the sex ducts the 

 epithelium is clearly not ectodermic in origin although histo- 

 logically it resembles the cuticle and is connected with it through 

 the cirrus pouch. 



In their histological structure, the walls of the uterus, oviduct 

 and seminal receptacle are made up of a simple layer of flattened 

 cells probably with a basement membrane. The oviduct fur- 

 nishes exception to this statement at its opening into the ovary 

 where a layer of circular muscle fibers is demonstrable, and in 

 that part of its course which is known as the fertilization canal. 

 In this latter canal the structure more nearly resembles that of 

 the vagina. The vagina beginning at the lumen consists of 

 ciliary projections, a layer of nuclei embedded in a homogeneous 

 cuticle, longitudinal and circular muscle fibers and a cellular 

 layer. 



These canals develop fairly quickly and have all (uterus ex- 

 cepted) finished their growth as far as cell division is concerned 

 long before the sex products call for their use. Upon the passage 

 of the eggs from the ovary they degenerate and their place is 

 taken by the embryo filled uterus. 



Whether the ducts grow by more and more parenchymal nuclei 

 becoming involved in the proliferating area, as Child thinks, 

 rather than by the actual outgrowth of the original anlage by the 

 multiplication of its cells is not clear to me. It seems probable 

 that the extension occurs by both methods of growth. The ovi- 

 duct and the vitello duct are unquestionably formed by the 

 differentiation of part of the cells in the primary anlage for it is 



