HEAD-MUSCLES IN GALLUS AND OTHER SAUROPSIDA. 525 



view — that the muscle plates of the head are serially homo- 

 logous with those of the trunk and somatic^is probably the 



sternohy 



post my/o. 



gon.hyo/d 



Text-figs. 18 and 19.— Sagittal sections tlirougli an embryo of 

 Chelone, in " stage 4 " of Parker. 18 is the more external. (For 

 explanation of lettering see p. 555.) 



true one, I shall assume that those of Lacerta are also 

 somatic. It will be seen later that the changes undergone 



