150 



s. GOTO. 



taneous displacement (^f the latter from the base of tlie penis 

 towards its top; so that tlie cavity of the })enis is morphologic- 

 ally speaking as much the external surface of the body as 

 the genital atrium, and the prostate glands are therefore to be 

 regarded as a s])ecial modification of the dermal glands, — a view 

 clearly in accordance with some facts observed in Temnocephala.^^ 

 The tissue of the large papilla projecting into the genittd atrium 

 at the top of which the vas deferens opens in HexacoUjlc is not 

 bounded off from the surrounding mesenchyma; but that it is 

 the homologue of the penis will, I believe, scarcely be contested 

 by any one. In Monocotijlc (PL XVIII, fig. 3), on the other 

 hand, the connective tissue that forms the substance of the penis 

 h:is undergone some transformation, having become fibn^us with 

 the fibres arranofed at risfht angles to the internal and ex- 

 ternal limiting membranes of the penis. It is, however, not yet 

 distinctly separated from the surrounding mesench3^ma by a mem- 

 brane. The penis encloses, in this genus, a tubular, chitinous 

 organ — the cliitinous penis — which is attached to it at the bottom of 

 its cavit}', and into which the vas deferens opens. This chitinous 

 ])enis is regarded by St.-Iîemy-^ as the transformed terminal portion 

 of the vas deferens. It seems to me, however, to be more in accordance 

 with ficts to regard it as the prolonged portion of the inner limiting 

 membrane of the penis, which has then undergone a chitinous trans- 

 formation ; and as tliis limiting membrane is morphologically no 

 other than a portion of the lining membrane of the genital atrium, 

 which is again but the invaginated portion of the investing 

 mendjrane of the body, the chitinous penis is, in my opinion, to 



]). Hasvveil— On Teuinocephala, au Aljerraut Mono,:^enetic Trematode. Quart. Journ. of 

 Mic. S3., vol. 28, 18S8. p. 28S. 



2). St.-Remy— /. c. p. 21.. 



