1 66 GARDINER. [Vol. XI. 



coincident with these changes the cells E^^i', E^l, E\r, E\l 

 are formed. Fig. 20, which is a view of the right side of the 

 ovum, shows Errand E'^r, and in Fig. 21, which is a diagram 

 of this stage, and treated as if transparent, E4/ and E'4/ are 

 shown by dotted lines. Apparently these cells arose from a 

 division of Eir, E\l, E' ir, ^"'1/ respectively. 



After this the ovum having attained a thirty-eight-celled 

 stage goes into its characteristic resting stage and the cell 

 outlines become obscure. During the next period of activity 

 the ovum reaches a sixty-six-celled stage, apparently in the fol- 

 lowing manner. It is, however, almost impossible to identify 

 with absolute certainty the order in which the cells divide. It 

 appears, however, that Di'i divides so as to give rise to Dri.i 

 and Dn.2 (Fig. 22 and 26); Drz into Drz.i and Drz.z ; Dr^ 

 into i^?'3.i and Dr^^.z ; Dh into Dli.i and DI1.2 ; BI2 into DI2.1 

 and DI2.2 ; DIt^ into i^/3.1 and Dl^.z ; D'ri into D'ri.i and 

 B'ri.2 ; D'r2 into D'r2.i and D'r2.2\ D'r-^ into D'ryi, D'ry2 ; 

 D'li into D'h.i and D'li.2 ; D'h into D'l2.i and D'12.2 ; D'l^ 

 into DHyi and D'ly2 ; making in all twenty-four cells derived 

 from D and D' . The cell Eir divides into Eiri and Eir2 ; 

 Ezr into E2i'i and ^2r2 ; £"4^ into E^ri and £"4r2 ; ^1/ into 

 ^i/i and £"1/2 ; E2I into ^2/1 and ^2/2 ; E^l into ^4/1, ^4/2 ; 

 E'lr into ii'in and E\r2\ E 2r into ^'2^1 and ^'2^2; ^'4;' 

 into if'4ri and E' ^1-2 ; ^%/ into E \l\ and £''1/2 ; £"'2/ into E zh 

 and £"'2/2 ; E\l into ir'4/1 and E^h. The cells -£"3 and ^'3 

 have not divided, but including them the total of the derivatives 

 from .£■ and E is twenty-six cells. B\ also divides into B\.\ 

 and Bi.2 ; B2 into ^2.1 and ^2.2 ; E i into ^'i.i and E 1.2 ; 

 ^'2 into Z>"2.i and ^'2.2, which together with ^3 and ^'3 make 

 ten cells derived from B and B^ . 



Fig. 26, which is a diagrammatic representation of the sixty- 

 six-celled stage (Fig. 22), shows the manner in which this stage 

 has been derived. The dotted lines represent the cells on the 

 opposite side of the ovum. It will be seen that / represents 

 the cells A and A^ from which B, B\ C, C, D, D\ and E, E 

 have been budded off successively. The ten derivatives from 

 B and B^ are shown in // ; in /// are the four derivatives from 

 C and C^ \ in /F the twelve derivatives from D\ in F the 



