744 ANATOMY OF VERTEBRATES. 



gestation is fifty-five or fifty-six days ; and she brings forth 

 usually from four to six young. 



In the Lioness the exterior of the placenta is marked by 

 anfractuosities like those of the brain ; the inner surface is divided 

 into small irregular convex lobes by deep sulci. In the zonular 

 placenta of the Dog the maternal portion cannot be defined and 

 separated as in the Cat : the uterine surface to which the placenta 

 adheres presents a finely reticulate substance, the meshes being 

 formed by orifices of apparently utricular glands, aggregated in 

 the interspaces of larger alveoli, scattered over the surface with 

 intervals of between half a line and two lines. When the foetus 

 has attained a length of five or six inches, this alveolar decidua 

 has acquired a thickness which makes it recognisable as the 

 maternal portion of the placenta. The period of gestation of 

 the Wolf, Jackal, and Dog is 63 days. 



A modification of the annular placenta, analogous to that in 

 the Elephant, obtains in some Carnivores, e. g. the Weasel tribe 

 (fig. 579, Putorius Furo); two portions of a subcircular form, 

 a, b, appear as a double placenta, but they are united by a 

 much thinner tract, c, also receiving ramifications of the allantoic 

 vessels. The umbilical cord, one-third of an inch in length, goes 

 to one of the cotyledons, whence the vessels extend to the other. 

 The omphalo-mesenteric 

 duct expands into a py- _.-.'-' 9 .__ 



year. In the Martens 

 the placenta is undivi- 

 ded {Mustela martes, M. foina, &c.) ; the decidua serotina 

 sinks into its substance along a narrow tract at the middle of the 

 outer surface of the zone, as in the Elephant : they bring forth, 

 commonly, twice a year, but are less prolific than the Weasels. 

 The navel-string is very short : the allantois is more elongated ; 

 a trace of vitellicle may be seen in a small bilobed yellowish 

 patch, upon the inner surface of the placenta, where the navel- 

 string ends. 



In the Hyaena the deciduous substance becomes fused with 

 the chorionic placental processes : it is moderately thick, spongy, 



Foetus and Tlacenta. Putorius Furo. cxxn'. 



