Proceedings of the Royal Physical Society. 



VI. On a Tract of modified Efitlielium in the Einhryo of 

 Sepia. ]3y William E. Hoyle, Esq., M.A. 



(Read 16tli January 1889.) 



On examining recently a number of serial sections of 

 embryos of Seioia, I was struck by the presence of certain 

 peculiarly modified ectodermal cells, and as the presence of 

 these has not, so far as I am aware, been hitherto recorded, I 

 propose in the following paragraphs to give a brief notice of 

 the appearances presented. 



The cells form a trifid tract (fig. 1) situated towards the 



Tig-l. 



B-.i:. 



Fig. 1. Dorsal view of an embryo of Sepia, to show the three lines of 

 modified epitlielium. 



Fig. 2. Transverse section of an embryo at abont the same stage of develop- 

 ment, to show the positions of the modified bands. 



Fig. 3. Transverse section of one of the fins showing the lateral tract. 



Fig. 4. Transverse section of the median tract, 



Bl, blood vessels ; Ca, cartilage, and probably muscles also of fin ; Co, con- 

 nective tissue ; Ej), unaltered dorsal epithelium ; ^^j^, epithelium of ventral 

 surface of fin ; L, lateral tracts of modified epithelium ; M.E.^ median tract ; 

 Sh, cavity of the shell ; Y, yolk masses. 



posterior aspect of the body ; the three branches of which 

 lie, one in the middle dorsal line, and one on the dorsal 

 surface of each fin, about midway between its origin and its 



