ANATOMY OF VERTEBRATES. 



go: they may not be thrown off together, and the maternal 

 decidua may not be shed all at once, but in successive shreds or 

 tags. The long gestation required to bring to due strength the 

 young of the defenceless hoofed animals before birth, is the con- 

 dition of the firmer texture, better organization, greater extent, 

 and more persistent character of their * deciduous ' structures. 

 The villi of the foetal cotyledons offer varieties of form and 



mode of termination, beauti- 

 fully illustrated by Gift in 

 xxviii. vol. iii., tab. CLXXi., 

 and indicated by Home, 1 as 

 follows : — 



' Bos — terminales ramosse : 

 Cervus ,, indivisse filiformes : 

 Ovis „ ,, villosse: 



Capra „ „ pilosae :' 



terms which, though not 

 strictly accurate, indicate the 

 degree and way in which 

 generic variety manifests it- 

 self in the cotyledonal modi- 

 fication of placental struc- 

 ture. 



About eighty cotyledons 

 are developed from the chorion of the Cow ; the surface of the 

 large uterine caruncles is usually flat or slightly concave. The 

 gestation of the Cow is about nine months (286 days), with a 

 range of variety of about twenty days. 



In the Red- deer ( Cervus elaphus) gestation is eight months and 

 a few days : the rut is usually in the last three weeks of Sep- 

 tember ; the birth in May or early in June. The foetus is long 

 confined to one uterine horn : the mucous layer of the allantois 

 forms a crescentic bag, the horns being prolonged into both those 

 of the uterus and ending obtusely : it contains a milky fluid, 

 depositing a sediment. The cotyledons are relatively smaller, 

 more oblong, and much fewer than in the Cow. The same may 

 be said of the Fallow-deer, the gestation of which is eight 

 months. Both species of Cervus are uniparous, as a rule. The 

 little Roe-deer usually brings forth twins : sometimes both come 

 from one ovary, more often one from each. The gestation here 

 is about nine months (280 days). The rut is in July and begin- 

 ning of August : impregnation and the cleavage-process goes on 



Portion of chorion with cotyledons, Cow. 



1 xxvni. in. p. 560. 



