No. 499] SUCCESSION OF SOMITES IN CHICK 469 



Fig. 2 shows the same embryo after nineteen more 

 hours of incubation. The heart was beating when the 

 egg was opened. The embryo was preserved in picrosul- 

 phuric-acetic acid, stained in Conklin's picro-haema- 

 toxylin, and mounted in xylol balsam. The drawing was 

 made with the aid of the Abbe camera. 



The first right somite is noticeably 

 smaller than its fellow on the left, y£5^k 

 there is no break between it and the /f U 



mesoderm in front, and only the pos- //' S 



terior part of it shows the radial j \ J 

 arrangement of cells which is char- j / i / 

 acteristic of the normal somite. The f. 

 scar of the operation shows at the WSm a j 

 side. A deeper examination in this *]S&?p!r 

 region reveals, mediad of the scar, a \\ 

 clear area extending into the limits of ; ; ^\u 1 ; 

 hotli the first and the second somite of V ... 



that side, indicating that the injury fjj *f i 

 reached inward from the point of i; ]h 

 entrance of the needle. The second \\ ]i I' 

 somite is also incomplete on its dorsal 

 anterolateral corner, as shown in the 

 figure. Except for these injuries and 

 the bend to the right which may have 



till-. 



being the result of p 

 coven-glass. 



Whatever else thi 

 proved, it showed ch 

 more than two somites 

 front of the one which 

 shut out at once the hy 

 who assumed that thr 



This of course 

 er and Benecke, 



A|>pl\ ing Miss Piatt's description of the order of ap- 



