340 



F. H. EDGEWORTH 



the separation has occurred in these also. In a 27 mm. embryo 

 the lower ends of the Constrictors have grown forwards. Each 

 is attached to the lower end of the Ceratobranchial of the 



Text-figs. 15-17. 

 Embryo 13-5 mm., transverse sections ; Text-fig. 15 is the most 

 anterior ; Text-fig. 17 is .32 ju behind Text-fig. 16. 



Trcuia. v&nt.//' 



perLCarcL 



Text-fig. 16. 



Leyat, 



Leyatv, 



Leval./v 



S*gULcl&fb 

 Ceralobr. v 



/ I \ \ '^ inzns.ventv 



Subarc.reot.v Tnxn^.vejit.v perLCixrcL. 



next anterior arch — the condition described in the adult by 

 K. Fiirbringer. 



The above-recorded observations show that the Constrictores 

 branchiales are the direct descendants of the branchial muscle- 



