( ^0 ) 



ducts are lateral (and caudal) of the Wolflian. Now it is obvious 

 that if my observation holds for marsupials generally, no masculine 

 uterus can arise, because between the tw^o Miillerian ducts those 

 of Wolff are found. Eventual remnants of Miillerian ducts will 

 have to be sought for in the male sex laterally of the terminal 

 opening of the vasa deferentia. I have not yet been able to make 

 observations of my own concerning this point. 



As I have already stated, the ureters, at the stage I observed, lie 

 at the medial side of the genital cords. Only those parts of the 

 female genital apparatus of the marsupials which lie at the lateral 

 side of the ureters, can, as I shall try to prove more fully elsewhere, 

 have their homologa in the female genital system of the monodelphic 

 mammals. The vaginal caecal sac developing phylogenetically in the 

 marsupial group, has no homologon in the female sexual organ of 

 the Monodelphia. 



Finally, I think, my obsei-vation contains an explanation of the 

 peculiar hook-shaped course of the terminals of the ureters of 

 marsupials. 



Either as a consequence of the spiral course of the Wolffian 

 ducts, or for some other cause, the ureters at a certain stage of 

 development lie medially of the Wolffian ducts (and of the genital 

 cords) in a dorso-cranial direction towards the primitive kidney. 



Marsupials possess a milk-nutrition (intestinal) at such an early 

 stage of development as is known of no other mammal. This milk- 

 nutrition will have a great influence on the development of the 

 bladder which I found as a very voluminous organ in the marsupial 

 young one described, as well as in other specimens (Didelphis) 

 examined by me. With the rapid growth of the bladder the orifices 

 of the ureters are at the same time displaced cranially. The above- 

 mentioned cross-connection between the two genital cords is an 

 obstacle to the cranial displacement of the ureters, the natural conse- 

 quence of which is that the ureters have always to go round the 

 caudal end of this bridge, while their orifices are further displaced 

 cranially, the result of which is the pronounced hook-shaped course. 



Zoology. — "A7i interesting Case of Reversion." By Dr. P. P. 



C. HOEK. 



PoUicipes and Scalpellum are two nearly related genera of pedun- 

 culate Cirripedes mainly differing from one another, by the one having 

 in its capitulum a restricted number of valves (Scalpellum) and by 

 the other having a much larger number of such calcareous parts 

 (Follici^jes). 



