EXAMINATION OF CYSTICEECOID STAGES 167 



three in either direction, run forwards into the proboscis and back- 

 wards into the trunk. 



The only other parts of the internal structure which are visible in 

 the living specimen are the sexual organs. Very little of these can 

 be seen, however, in sexually mature females, the body-cavity being 

 more or less completely filled with germinal cells, cell masses, and 

 eggs enclosed in shells. In the middle of the body of the male the 

 two oval testes will be seen, placed one behind the other. Their 

 ducts, which are directed backwards, are seen to combine and are 

 surrounded by the cement glands, club-shaped bodies, usually of a 

 very dark colour. Beyond the cement glands the vas deferens passes 

 into the muscular penis, which is withdrawn into the genital bursa. 

 The bursa is a bell-shaped organ situated at the posterior end of 

 the body, with an orifice communicating with the exterior. It is 

 occasionally seen to be everted and in this position it plays a definite 

 part in the act of copulation. The genital opening of the female is 

 also situated at the posterior end of the body. 



In the young female, the ovaries are in a position analogous to 

 that of the testes in the male, but they soon break down into a 

 number of cell agglomerations, known as " loose " or " floating " 

 ovaries, and sometimes termed " placentulae." At the period of sexual 

 maturity, successive single cells (egg-cells) are released and, after 

 fertilization, these develop within the body-cavity into the eggs. The 

 latter are usually spindle-shaped ; they are enclosed in three shells, 

 and they contain a finished embryo. They more or less completely 

 fill the body-cavity, concealing the apparatus by which they are 

 ejected, the orifice of which is situated at the hinder end of the body. 

 This apparatus should be studied in young females, or a mature 

 female may be opened longitudinally and all loose structures removed 

 by means of a water-jet, when a long, cordlike structure will be seen. 

 This should be removed and examined separately, when it will appear 

 as a tube, open at both ends, and divided into three parts of unequal 

 length. The central portion, the uterus, is the longest ; it is pro- 

 longed backwards into the short vagina which communicates with the 

 exterior, while its anterior end is continuous with the bell, an organ 

 whose shape varies in different species. The bell is provided with 

 three openings : one placed anteriorly and opening into the body- 

 cavity ; one placed posteriorly and opening into the uterus ; and a 

 third, which is situated in the ventral wall. The bell-wall is muscular 

 at its anterior end but becomes cellular before passing into the uterus. 

 It performs certain swallowing movements which may be seen by 

 examining the freshly removed organ, together with a portion of the 

 body contents, in white of egg. By means of this movement the bel 

 swallows a number of the bodies floating in the body-cavity and 



