222 



r. H. EDGEWOIM'II, 



liyoideus has separated from and extendetl upwards outside the 

 anterior digastric, Avhich has grown a little forwards. In 10 

 nun. embryos the anterior end of the anterior digastric has 

 reached Meckel's cartilage, the interhyoideus has extended 

 forwards, and also backwards in the neck forming the platysma 

 colli, and the stapedius has separated from the Anlage of the 

 posterior digastric and stylohyoid. In 13 mm. embryos the 

 Anlage of the postei-ior digastric and stylohyoid has separated 

 into those muscles, and the lateral edge of the fore part of the 

 interhyoideus (Text-fig. 96) has extended upwards and for- 



Text-fig. 49. 



Text-fig. 49. — Cevatodus, euibryo 15 niiii. ; portion of transverse 

 section taken between the fifth branchial segment and the hnig. 



wards forming the platysma occipitalis and ])latysnia faciei. 

 The posterior digastric forms a tendon (vide Krause). 



There is thus in the rabbit a stage of development prior to 

 the first described in man by Futamura, in which the Anlage 

 of the platysma faciei, platysma occipitalis, and plat3sma 

 colli is a structure homologous with the interhyoideus of lower 

 forms. The anterior digastric is homologous with the hyo- 

 maxillaris of some Ani]diibia and Teleostomi. 



The Homologies of the Hyoid Muscles. — In Alytes, 

 Bufo, l{;ina, Pelobates, and Lepus, the lower end of the hyoid 

 myotome becomes separated from the part above and forms 

 a longitudinal muscle — the hyo-maxillaris — connecting the 

 hyoid l;ar with the lower jaw. An homologous muscle is 



