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Dr. M. Watson. 



numerous authors in other species of mammals. The fact, moreover, 

 that the intra-placental prolongations of maternal mucous membrane 

 were invested by such a layer of cells lends additional support to this 

 opinion. 



I have already remarked that, with the exception of its epithelial 

 layer, the mucous membrane of the gravid horn of the uterus, sub- 

 sequent to detachment of the placenta, was quite entire, and that the 

 uterine surface of the placenta was not invested by a complete layer 

 of decidua serotina, such as is met with in the shed placenta of the 

 cat.* In Procyon, therefore, the intra-placental prolongations of 

 maternal mucous membrane, together with the epithelium, are alone 

 deciduous, the mucous membrane of the uterus remaining adherent 

 after detachment of the placenta. 



Comparison of the Placentation of Procyon with that of other Car- 

 nivores. 



From the particulars above detailed, it will be seen that Procyon 

 agrees with the other carnivorous mammals, with the placentation of 

 which we are acquainted, in respect of the annular or zonary form 

 of its placenta. This form of placenta, and this alone, has been met 

 with in the various members of the group Carnivora, the placentation 

 of which has hitherto been examined. In the majority of these the 

 placenta forms a complete zone, and presents no trace of the placental 

 gap which, in Procyon, occurs at that part of the placental band 

 which lies in relation to the dorsum of the embryo. The gap in 

 question has, however, been observed in the placentas of a few car- 

 nivores. So far as recorded observations go, while failing to 

 recognise the presence of this gap in the placenta of any digitigrade, 

 or pinniped Carnivore, they have affirmed its presence in the placenta 

 of every member of the plantigrade section, the placentation of which 

 has been hitherto examined. The latter group includes the genera 

 Martes, Mustela, and Lutra, in the members of each of which a 

 placental gap has been observed. With these, therefore, Procyon 

 agrees more closely as regards its placentation than with any member 

 of either the digitigrade or pinniped groups, in the placenta of none 

 of which does the gap in question occur. If BischofPs explanation of 

 the formal ion of this gap be correct, it would appear that, in the planti- 

 grade Carnivora, the closure of the true, and the consequent separation 

 of this from the false amnion takes place at a relatively later date in 

 the latter than in either the digitigrade or pinniped Carnivora. 



But, whilst the placenta of Procyon differs, in this respect, from 

 that of the members of the digitigrade and pinniped groups of Car- 

 nivora, it agrees with them in its truly deciduous character, as exempli- 



* Eschricht, " De Organis," pp. 14, 18 ; and Turner, " Lectures on the Com- 

 parative Anatomy of the Placenta/' p. 80. 



