44 o DISCOVERY REPORTS 



more clearly by some such set of organs as the genital system, rather than by such parts 

 as the skeleton, limbs or teeth, which are the most directly influenced by the animal's 

 immediate environment. The viscera will tend to remain constant in their morphology, 

 while the parts of the body in more direct contact with the environment are undergoing 

 evolutionary changes. 



The urino-genital system of the Cetacea presents many extremely primitive and 

 striking features which it is one of the aims of this paper to emphasize. In the female 

 system the following may be noted : 



(i) The ovary lies free upon the ligamentum latum and is not enclosed in a peritoneal 

 sac. This may be taken to be a primitive character, since the development of any sort of 

 covering must be a specialization. The absence of any such covering, however, is rare 

 among mammals. In Monotremes there is a pouch formed by a ligament connected to 

 the peritoneum which forms the ovarian capsule, and in the camel, among Artiodactyle 

 Ungulates, the ovary lies in a pavilion provided by the oviducal funnel. This has been 

 noted also in some Cetacea. In the Ruminants the ovary is lodged in a recess or sacculus 

 of the broad ligament as reported by Turner (18706) for Orchitis. In other groups of 

 mammals the ovaries are enclosed, sometimes completely, in a peritoneal sac or 

 "tentorium". 



(ii) The ovary is suspended in the abdomen by means of a plica diaphragmatica, 

 attached to the body wall lateral to the kidney and extending nearly to the diaphragm. 

 This is the primitive method of attachment of the mammalian gonad, and is found best 

 expressed in Monotremes and Insectivores. 



(iii) Multilobulation of the ovary. Anthony (1926) pointed out that this is a primitive 

 character found in many other mammals. The polyoestry — shedding of the ova outside 

 the usual breeding season — is also a primitive character. 



(iv) The complete absence of accessory glands. This is also a feature of the male 

 system. 



Besides these characters, which may be regarded as primitive, there are others which, 

 while not primitive, are shared by other groups of mammals and are distinctive of the 

 Cetacea and of those groups. 



In the female system the following may be noted : 



(i) The uterus bicornis, short corpus uteri and the absence of a well-defined os uteri 

 have already been mentioned. The presence of a uterus bicornis is a fundamental 

 character and narrows the comparison down to three groups of mammals which also 

 have this form of uterus — namely the Insectivora, Carnivora and Ungulata. The short 

 corpus uteri and the presence of the circular folds in the vaginal wall are found, among 

 these groups, only in Insectivores and some Perissodactyle Ungulates (Rhinoceros). 

 In the camel among the Artiodactyles the uterine wall is folded at the union of the uterus 

 and vagina, but there is no folding of the wall of the vagina itself. In other Artiodactyles 

 there is a well-marked os and no folding of the vaginal wall. 



(ii) The separation of the urinary and genital openings. As has already been stated 

 this occurs in some Insectivores, many Rodents and some Prosimiae. In all these groups, 



