294 PROFESSOR ROLLESTON ON THE 



fied in substituting for " le Furet Putois " the words " la belette Mustela ; " and Dau- 

 benton's words, which we append, will show that he is scarcely justified in speaking of 

 this creature as furnishing an instance of a double placenta, such as that which we find 

 in the Old-World Simiadee (p. 220), " Chaque foetus avoit deux placentas ronds, poses 

 sur une zone circulaire qui embrassoit le foetus sur le milieu du corps, comme les 

 placentas du Chien et de la Fouine. Les placentas du Furet avoient chacun environ neuf 

 a dix Ugnes de diam^tre et une ligne d'epaisseur dans le niiheu. Leur face exterieure 

 etoit grisatre, et I'interieure avoit une couleur rougeatre. lis n'etoient eloignes I'un de 

 I'autre que d'une ligne par I'un des cotes et d'un pouce par I'autre cote ; ce dernier infer- 

 valle etoit rempli par une sortc de placenta, car la substance qui s'y trouvoit etoit beaucoup 

 plus epaisse que celle du chorion et celle de Vamnios." 



Rodentia. 



The following history will show that in the Rat, and probably in all other Rodents, 

 the three structures which we have called placenta, deciduous serotina, and non-deci- 

 duous serotina are as distinct from each other as they are either in the Cat or in the 

 Tenrec. A female Rat (Mus decumanus) was killed after giving birth to nine fcetuses. 

 Of these, three had been partly devoured by the mother to the extent of one-third or so 

 of their whole bodies, beginning in two cases from the head and in the third from the 

 tail. The stomach of the mother was found to contain, besides the food furnished to 

 her and the portions of the foetuses just specified, the placentas or a great number of 

 the placentas which had been in connexion with the nine foetuses. Some of these 

 placentas had upon the convex surface a cap of pulpy decidua serotina with a thickened 

 border; in others this cap was removed, and the placenta, from exposure to the mace- 

 rating action of the digestive juice, had its villi hanging free, and presenting an arbo- 

 rescent appearance. Portions of decidua serotina were found in the stomach lying loose 

 by themselves. Some of the placentae had cords of about an inch in length in connexion 

 with them. 



Along one uterine cornu there were found six, and along the other there were found 

 three globular masses forming hernial protrusions either into, or by the side of the 

 mesometrium, and marking the places of attachment of the nine foetuses. A vertical 

 section of one of these lateral dilatations, together with the uterine tube to which it is 

 appended, is given in PI. L. fig. 8. The cavity of the uterine tube is covered with a 

 corrugated mucous membrane ; at its mesometrial border a funnel-shaped depression, also 

 covered with this corrugated mucous membrane, leads down to the hernial protrusion, 

 or globular dilatation, which is formed by the non-deciduous serotina (p s) and the 

 circular muscular coat (c m) with which the utero-placental mucous membrane is more 

 intimately connected in the Rodents than in any of the three orders we have as yet 

 spoken of, and in the interstices of which much mucous tissue is contained. A pro- 

 jecting process (u p) of corrugated non-placental membrane marks the line where a 



