THE EARLY DEVELOPMENT UT THE MAKSLPJALIA. 121 



the uterus. . . . The embi'vonic evidence of the common 

 origin of Mammalia and Sauropsida, both as concerns the 

 formation of the layers and of the embrvonic membranes is 

 as clear as it can be.''' 



That view of the derivation of the Mammalia receives, I 

 venture to think, striking confirmation from the observations 

 and conclusions set forth in the preceding pages of this 

 memoir, and from it as a basis all attempts at a phylogenetic 

 interpretation of the early ontogenetic phenomena in the 

 Mammalia must, I am convinced, take their origin. Such an 

 attempt I have essayed in the foregoing pages, with what 

 success the reader must judge. 



Addexdcm. 



The memoir of Prof. 0. Van der Stricht, entitled ''La struc- 

 ture de I'oeuf des Mammiferes (Chauve-souris, Yesperugo 

 noctula) : Troisieme Partie " ('Mem. de I'Acad. roy. de 

 Belgique,' 2ud ser., t. ii, 1909), came into my hands only 

 after my own paper had reached its final form, and therefore 

 too late for notice in the body of the text. In this extremely 

 valuable contribution, A^au der Stricht gives a detailed 

 account ot the growth, maturation, fertilisation, and early 

 cleavage-stages of the ovum of Yesperugo, illusti-ated by a 

 superb series of drawings and photo-micrographs. All I can 

 do here, however, is to direct attention to that section of the 

 paper entitled '" Phenomeues de deutoplasmolyse au pole 

 vegetatif de I'oeuf" (pp. 92-96), in which the author describes 

 the occurrence in the bat's ovum of just such a process of 

 elimination of surplus deutoplasmic material as I have 

 recorded for Dasyurus. Yan der Stricht's interpretation of 

 this phenomenon agrees, I am glad to find, with my own. 

 He writes (pp. 92-93) : " Ce deutoplasme rudimentaire, a 

 peine ebauche dans I'ovule des Mammiferes, parait etre 

 encore trop abondant dans I'oeuf de Chauve-souris, car ces 

 materiaux de reserve, en partie inutiles, sont partiellement 

 elimines, expulses de la cellule." 



