EEPRODUCTION. 



83 



Fig. 85. — PcetuB of mare with its envelopes. (Chauveau.) A, chorion; C, amnion re- 

 moved from allantoid cavity and opened to expose fcEtns; D, infundibalum of 

 urachas; B, allantoid portion of nmbilical cord. 



other than the monotremes and marsupials have a true allan- 

 toic placenta. 



The Discoidal Placenta.— This form of placenta is that exist- 

 ing in the rodentia, insectivora, and cheiroptera. The condition 

 found in the rahhit is that which has heen most studied. The 

 relation of parts is shown in Fig. 79. 



The uterus of the rodent is two-horned ; so we find in gen- 

 eral several emhryos in each horn in the pregnant rahhit. 

 They are functionally iudependent, each having its own set of 



