52 K- MITSUKÜRI; 



what and destined to rise still more that is to form the 

 tail-swelling. On comparing this section with /), it is 

 found that the shoulder-like mass in c corresponds to 

 that part of the mesoblast in h which is marked off as 

 the mesoblastic somites. The lateral plates of the meso- 

 blast are therefore out of the area of elevation. 



d is nine sections behind c. The " Endwulst " mass is 

 smaller than in c, but stands out more prominently and 

 shows more distinctly that it is rising up. The lateral 

 plates of the mesoblast are not included in the elevation and 

 are left below. The foreûfoino: section and this one show 

 that the tail- sir ell iu g is not jyroditced Inj foldifuj, hut hij tlic 

 groirth 2ipwards of the '^Endiridst'" mass. If it were produced 

 by f )lding, the lateral plates, for one thing, ought to be near 

 the dorsal surface of the "Endwulst" instead of being 

 down below, as in this section. Ikit of this more in some 

 of the following series. The epiblast is very much thick- 

 ened outside of the " Endwulst." The middle of the 

 three concentric zones of the superficial view, (Fig. 25), 

 I believe, corresponds with tliis thickened zone of the 

 epiblast. 



e is three sections behind d. The great thickness of the 

 epiblast in this section is due to the fact that the thick 

 w^all of the epiblast such as is shown on each side of the 

 tail-swelling in d goes entirely around its posterior end 

 and this section just goes through this wall. jSTote that in 

 all the sections in front of, and including, this, the epiblast 

 is entirely independent of the layers below. A comparison 

 with Series YI show\s that the primitive streak, which ex- 

 tended in an earlier stage over the " Endw^ulst " (VI, ^.), 

 has now disappeared from that part. Of this, more anon. 



f is two sections behind e and is the second in which the epi- 

 blast is united with the layers below it. 



g is two sections behind /. The coelem now runs nearly 

 across, dividing the mesoblast into the parietal and vis- 



