MORPHOLOGY OF CKANIAL MUSCLES IN SOME VEUTEBRATES. 191 



which joins the temporal (Text-tig. 60) and the otlier the sub- 

 temporaL 



The muscles of Alytes, Bufo leutigiiiosus, and Pelo- 

 bates' ai-e siinihir to those of Rana (Text-fig. 63)^ except that 

 the extra-temporal is inserted only into the superior labial 

 cartilage. 



The Anlage of the levator bulbi is given off from the upper 

 surface of the hinder part of the temporal in 9 mm. hirvas ; 

 its outer end becomes inserted into the skin and upper edge 

 of the palato-quadrate bar ; it remains relatively undeveloped 

 until late in metamorphosis. On the development of the lower 

 eyelid a slip is separated from the levator bulbi^ forming the 

 depressor palpebra3 inferioris. 



At metamorphosis, on the atrophy of the superior labial 

 cartilage the sub-temporal and exti-a-temporal fuse with the 

 temporal, and the muscles become more vertical in position 

 on the rotation of the palato-quadrate bar. 



The Anlage of the intermandibularis of Rana divides in 

 7 mm. embryos into three parts — the submentalis, the man- 

 dibulo-Iabialis, and the submaxillaris. The submentalis 

 develops later than the other two muscles ; in 12 mm. embryos 

 it forms a mass of small round cells lying beneath and 

 extending backwards from the inferior labial cartilages, and 

 at the beginning of metamorphosis forms a layer of trans- 

 versely directed muscle-fibres connecting together the infe- 

 rior surfaces of the inferior labial cartilages (Text-fig. 60). 

 The mandibulo-labialis, arising from the inner aspect of the 

 transversely directed MeckeFs cartilage, passes down external 

 to the genio-hyoid and is partially inserted into skin, partially 

 interlaces with the muscle of the opposite side (Text-fig. 60). 



The submaxillaris arises from the under surface of Meckel's 

 cartilage. The conditions in larvasof Bufo lentiginosus 



^ Tins aecoinit differs from that of Scliiiltze, in that the suljtemporal 

 is stated to he inserted into Meckel's cartilage as well as into the 

 superior labial cartilage, and in the description of an extra-temporal. 

 The results were obtained from serial sections of larva?, 10, 13. 22. and 

 30 mm. lony". 



