SOLEUO STOMA. 89 



are united only at the time of copulation. The male of Heteroura 

 androphora has also the habit of remaining connected with its 

 mate beyond the period of copulation ; here, thus, there is a con- 

 tinuous union of the two sexes without a growing together ; and 

 in Syngamus trachealis there is ultimately a lasting continuity of 

 the sexes by means of an actual growing together." 



Having entire confidence in Yon Siebold's statement, I am 

 bound to conclude that the sexual union in my specimens had only 

 recently been effected ; but, admitting tliis to have been the case, 

 one naturally asks in what manner can the mature eggs make 

 their escape, seeing that the vagina is blocked up by the intro- 

 mittent organ and bursa of the male ? Clearly the eggs can only 

 escape by an eventual breaking up of the body of the parent ; 

 this result, however, is quite admissible, as it constantly happens 

 in the cestode proglottides, where the vaginal orifice is too small 

 to allow of the escape of the eggs with their contained six-hooked 

 embryos. The eggs of Sclerostoma Syngamus are comparatively 

 large, measuring longitudinally as much as the -^o of an inch, 

 their transverse diameter being just half the above measurement ; 

 the length of the yolk is i-J from pole to pole. The process of 

 segmentation of the yolk accords with that observable in nema- 

 todes generally, the spherical cellules represented in the accom- 

 panying drawing (5, fig. 22) averaging a breadth of only ^^ of 

 an inch. The egg itself is oval, and bordered by two extremely 

 delicate and transparent envelopes, whose curvatures at either 

 pole are sHghtly interrupted, and the eggs consequently present 

 truncated ends when viewed in profile. Many of the ova contain 

 fully formed embryos ; and in the centre of the lower third of the 

 body of one of them I distinctly perceived an undulating canal, 

 probably constituting the, as yet, imperfectly formed intestinal tube. 

 By whatever mode the young make their exit from the shell, it 

 is manifest that prior to their expulsion, they are sufiaciently 

 developed to undertake an active migration. Their next habita- 

 tion may occur within the bodies of certain insect larv^ or even 



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