Arthur B. Lamb 



is: 



divides the anterior part into three smaller portions: one axial in 

 position, two lateral and paired. From these lateral portions develops, 

 on either side, the anterior head cavity of Miss Piatt. Of the axial 

 portion as much as lies beneath the infundibulum is aborted, while its 

 anterior part persists and forms a connecting stalk by which the somite 

 of one side is joined with that of the other. This connecting stalk is 

 similar to that (C. sf. in figures) which joins the first (premandibular) 

 somite of one side with that of the other. The only difference is that 

 there we have a canal, while here we have a loose and solid strand of 



0.5101 



Fig. 2. — Parasagittal section of somites A, I and II of Acantliias embryo of 16 

 mm. total length showing the early ditlerenliation of muscles inferior and superior 

 obliquus and inferior rectus. 



connective cells. It wdl be seen that Hoffmann differs from Miss 

 Piatt, simply in the recognition of an axial portion which later gives 

 rise to a connecting strand. Stages in which 29-33 somites were differ- 

 entiated showed very clearly the presence of this axial portion as de- 

 scribed and figured by Hoffmann. See also Minot's figures (oi, pp. 

 82, 83). 



At a 32 segment stage the somite is elongate in form, its main axis 

 extending obliquely downward beneath the eyeball. It is smaller at its 

 dorsal end, where the cells have assumed a somewhat epithelial arrange- 

 ment, and a slight lumen is present. Ventrally. the somite consists of a 



