452 THE PHYSIOLOGY OF REPRODUCTION 



it retains its thickness later in pregnancy. The deciduofracts 

 remain distinct to the end, though they partly degenerate. Hence 

 it is probable that during the whole, or nearly the whole, of 

 pregnancy they exercise a phagocytic action on the maternal 



I. in. 



i.l. 



n.v. - 



u.v 



FIG. 114. Transverse section through the uterus of Sorex at a stage when 

 the blastocysts are still in the oviducts. The coiled uterine glands (Gl.) 

 are massed together in the anti-mesometrial regions. The uterine lumen 

 (U) is more or less ^-shaped. (From Hubrecht's "The Placentation of 

 the Shrew," Quar. Jour. Micr. Sci., vol. xxxv., 1894.) 



B. V., blood-vessels ; c.m., circular muscle ; /.MI., longitudinal muscle. 



tissues, and store nutriment which they give up to the embryo 

 in a way as yet unknown. 



Shrew. In the shrew (Hubrecht l ) the method of embedding 

 is centric, and no decidua reflexa is formed. The yolk-sac pla- 

 centa is not so well developed as in the hedgehog. 



The attachment of the blastocyst is modified, as in Ruminants, 



1 Hubrecht, " The Placentation of the Shrew," Quar. Jour. Micr. Sci., 

 vol. xxxv., 1894. 



