224 BR. A. A. W. HUBRECHT. 



surella, Spondylus) there is a direct discharge of the genital pro- 

 ducts into the cavity of the kidney. In the next stage the 

 genital and urinary ducts open out upon the same papilla [Pinna, 

 Mytllus) ; in the remaining majority the separation has become 

 even more complete, and the external openings more distant ; 

 the primitive arrangement, in which ovary, pericardium, and 

 nephridium lead into one another in an unbroken order of suc- 

 cession, being retained in the Solenogastres alone. 



A reserve has to be made with respect to the male genital 

 products of Neomenia carinata. These are evacuated along sepa- 

 rate lateral ducts, provided with calcareous penes, and connected, 

 according to the observations of Koren and Danielssen (11) — 

 which have not yet been repeated — by separate vasa deferentia 

 with the hermaphroditic gland. 



Similar penes are absent in Proneomenia, and although only 

 two specimens have as yet been examined, it seems improbable 

 that they will afterwards be detected in others, as the specimens 

 under observation appeared to be true hermaphrodites, and not 

 simply females, both ova and spermatozoa occurring in parts of 

 the ducts (7). Nor has a similar arrangement been observed- 

 in Chatoderma or in the Chitones. 



It will be apparent from the foregoing, that further careful ob- 

 servations on the male genital ducts of Neomenia carinata, which 

 Koren and Danielssen confess to have only imperfectly made out 

 (11), as well as on the exact mode of communication between 

 the genital gland and the pericardium in this genus and in Chce- 

 toderma, are very much wanted. Furthermore, a comparative 

 histology of the renal organs, marked N in the woodcuts, will 

 have to be made. It must be remarked that in Chatoderma (fig. 8) 

 these organs open to the exterior separately, whereas they 

 coalesce into a single duct, with only one median opening, in Pro- 

 neomenia and Neomenia (figs. 9 and 10). 



The different accessory glands of the genital apparatus, which 

 have been described as such (7, 11), are here passed over in 

 silence, because in the present stage of our knowledge a com- 

 parison of these with each other would be premature. The ex- 

 amination of specimens in the fresh state will alone enable us to 

 form a sound judgment on these points. 



Nor are structures, such as the presumed byssus-like glands 

 of Proneomenia and Neomenia (7), the foot gland, &c., here 

 taken further notice of, because our knowledge is not yet far 

 enough advanced to admit of a fruitful comparison. 



In order to facilitate comparison of the woodcuts (1 — 11) in- 

 serted in this paper, with the different illustrations given by the 

 several authors on the Solenogastres of the genital and excretory 

 organs, &c., of these animals, I have added the following key to 



