14 GENERAL DEVELOPMENT OF THE EMBEYO. 



become markedly bilobed as compared with the previous stage 

 (fig. 36). 



Stage E (figs. 30 — 34). — In the next stage (fig. 31)^ which is 

 found at the end of September and early in October in England, 

 the spiral straightens out, and the embryo becomes bent double, 

 the ventral surface of the hind part of the body being applied 

 to the ventral surface of the front portion, and the tail end of 

 the embryo being curled round the front end of the head. The 

 bend occurs at the level of the eighth somite. 



An embryo straightened out and drawn from the side is 

 shown in fig. 30. 



The main features of this stage, in addition to the loss of 

 the spiral form, are — (1) the increase in the number and size 

 of the somites and appendages ; (2) the closure of the eye-pits ; 

 (3) the growth of the lips ; (4) the appearance of a groove in the 

 thickened ectoderm on the ventral surface of the praeoral lobes ; 

 (5) the presence of a well-marked dorsal projection at the level 

 of the anterior bend of the body ; (6) the beginning of the ecto- 

 dermal invagination which will form the stomodseum ; (7) the 

 appearance of a pit at the apex of the oral papillae (fig. 33, 

 or. p.) ; and (8) of a perforation on the hinder part of the 

 ventral swellings at the base of the oral papillae (fig. 33, o. s.). 



With regard to these points, I may make the following 

 observations : 



1. The antennae have become ringed, and the number of 

 somites is almost completed. There are ultimately twenty-one 

 somites ; in this specimen twenty could be made out (fig. 32) . 



2. In the specimen figured (fig. 30) the eye-pits were not 

 closed ; they remained open in this specimen abnormally late. 



3. The lip-fold has grown considerably, and extended on to 

 the ventral surface behind the jaws (figs. 30, 33, L.). 



4. These grooves are shown in fig. 35 (c. g.), which is taken 

 from a young specimen of the next stage. They are at first 

 wide and shallow, but, as we shall see, soon become deep and 

 narrow, and eventually closed. 



5. This projection had already appeared in the spiral stage 

 (figs. 28, 29), but it first becomes conspicuous iii this stage 



