58 



COMPARATIVE AXATn.MY. 



Ill ni(i>t cases ;i iiii'iliaii cartilaginous liar (i n t i/rt ra bee ul a is formed 

 between tlie tralieeuhu in front, fusing with theiii. and formim: tin- ellnuu-ii;i>ul 

 septum. It ocea.-ionally pr 'ji-cts forwards to i'orin a rostrum. 



We must now follow further the processes of growth, taking as 

 a foundation the primary condition of things described above, in 

 which the trabecula- havt- unii'-d together in the middle line. The 



Fl:. 43. DIAGRAMMATIC TlIANS V KKSF. SECTIONS, OF TIIK HEAD IN E.MIiRYO 



(A) STURGEONS, KF-ASMOBUAXCHS, ANUIIA, AND MAMMALS ; (B) UHODELES AXD 



SxAKF.s; AND ((.') C'EKTAIN TjELEOSTEAXS, LlZAKDS, CllOCODILKS, < 'll KI.oXI ANS, 

 AXD 



Tr, trabeculu? crauii ; G, brain : J, C}-es ; I'n, parasphenoid ; /,S', iuterovbital septum ; 



F, frontal ; Off, olfactory nerve. 



cartilaginous basal plate now comes into relations with the olfactory, 

 optic, and auditory organs by the formation of processes which 

 serve particularly in the case of the olfactory and auditory 



YJL 



Fie. 44.- SECOKD STACK IN Tin: I >r.\ i i .OI-MI \ r OF 1111: I'lUMoiiinAi. 



C, notochord : 11, li;i>il;u- jilatc : '!'', lr:il.n-iil:i, \\liii-li has >mitril with its fellow in 

 front of thr pituitary space \ fnini the cthninnasal sejitnni \N): ''/, cornu 

 trahi'i-uhe. Mini .//', aiiturbilal pri'i-s. \\hieh sn|i]nis thr nlfartcry organ (.\l\) 

 in front ami bchiml : /, foramina lor exit of tlie olfai-tory nerves from the 

 cranium; /'/', postorbilal pro. . >> of tialirciila ; A' A', Dasal eapsiile ; .-1 , eye; 



", MUditolV ea].slllc. 



a]i])avatns to connect the skull \\ith the cart ilaginous 



sulcs, and thus to act as sujtjtorts lor them. Thus an olfactorv, 



an orbital, and an auditory region are early differentiated. 



