GENERATIVE ORGANS OF VERTEBRATA. 



615 



Sometimes each spermatic duct opens on a papillif orm process (Saurii, 

 Aves). 



A rudiment of the Mullerian duct may sometimes be seen in the 

 form of a filament passing forwards from the anterior end of the 

 secondary kidney (Saurii), while further remnants of the anterior 

 portion of the primitive kidney which are not converted into the 

 secondary testis may be recognised. 



§ 454. 



In the Mammalia the generative apparatus undergoes great 

 metamorphoses, owing to the farther development of various portions 

 of the efferent ducts and the formation of a number of accessory 

 organs. In the female apparatus these are largely correlated 

 with the relations that obtain between the embryo and the maternal 

 organism. As this is least marked in the Monotreinata, they under- 

 go the least amount of modification, and have therefore direct 

 relations to the lower divisions of the Vertebrata, and especially to 

 the Sauropsida. The oviducts (Fig. 350, t) open separately into a 



Fig. 350. Female generative organs of 

 Ornithorhynchus. o End of the ovi- 

 duct and ovary, t Oviduct, u Uterus. 

 u' Point at which the orifice of the uterus 

 projects upwards, close below the openiug 

 of the ureter. vu Urinary bladder. 

 sug Sinus urogenitalis. cl Cloaca. 



Fig. 351. Female generative organs of 

 Halmaturus. ov Ovary, od Oviduct. 

 u Uterus, cv Vaginal canals, cug Sinus 

 urogenitalis. vu Urinary bladder. 

 ur Ureter, * Opening of the bladder. 



sinus urogenitalis, which communicates with the cloaca (cl). The 

 lower end of the oviduct, which is distinguished by the greater 

 thickness of its muscular wall, forms a uterus (u) ; but this merely 

 corresponds to the structures which likewise function as a uterus in 

 many Anamnia and Sauropsida. 



In the Marsupialia the efferent ducts of the female are connected 

 together on the outer surface, and each of them gives rise to an 

 oviduct and uterus, as well as to a new portion, or vagina, which 



