1226 



MR. F. E. WELLS ON THE MORPHOLOGY OF THE 



the purpose of naming the various cartilages present. The 

 explanation oflered in the figure does not explain the slight 

 constriction in the middle of the quadrate. 



It remains, however, without doubt that the quadrate, the 

 symplectic, stylohyoid, hyomandibular, and Meckel's cartilages, 

 all arise from the same single mass of cartilage, which mass was 

 originally fused to the cranial part of the skull, whereas the 

 palato-pterygoid cartilage arises entirely separated. 



Text-fig. 1 1 shows the development of the suspensory arrange- 

 ment of the jaws compared with that of Amia calva, and also 



Text-fio-ure 10. 



Lateral view of cliondrocranium. 50 mm. Stage. X 17. 



stages in Salmo and Syngnathus. This figure tends to fill in the 

 gap left by the absence of an}'' comparison in the text. 



To assist further comparison, the following table, showing the 

 rate of growth of the larva, is given : — 



Hatching , 4 mm . 



2 weeks 10 mm. 



1 month 18 mm. 



2 months , 35 mm. 



3 months 48 mm. 



4 months 55 mm. 



approx. 



(H. A. Meyer.) 



6. Summary. 



1. The hyomandibular, quadi-ate, symplectic, and stylohyoid are, 



in the 5 mm. stage, all one mass of cartilage. 



2. This mass is fused, at this stage, to the cranial cartilage and 



to Meckel's cartilage. 



3. The palato-pterygoid forms at about 13 mm., and grows back 



to meet the quadrate. 



