122 ON THK MORPHOLOGICAL CONSTITUTION OF 



bones to be the turbinal divisions of the olfactory " sense- 

 capsules ;" and, according to liis doctrine of the sense-capsules, 

 elements of the splanchno-skeleton. If Professor Owen under- 

 stands by the turbinal divisions of the olfactory sense-cap- 

 sules, bones homologous with the inferior turbinated, or even 

 the so-called ethmoidal turbinated bones of the mammal, it is 

 difficult to understand, on embryological principles, how, as 

 splanchnic bones, and as developed in connection with the 

 maxillaries, they come to be situated under the integument of 

 the upper surface of the head. It is, moreover, questionable, 

 whether the sclerous capsule of this, or of any of the special 

 sense-organs, is ever divided, and its parts separated from one 

 another, under such relations as those presented by the so- 

 called " turbinals" and " ethmoidal" of the osseous fish. 



The intermaxillaries form the principal and more peculiar 

 elements of this form of vomerine sclerotome. The nasal 

 fossa; being entirely absent, the merely fibrous olfactory sense- 

 capsule is subcutaneous, or partly under cover of the nasal 

 bones (turbinals) ; the vomer is not developed as a septum, 

 but merely to supply a fulcrum for the intermaxillaries, which 

 may even constitute the entire sclerotome, but are never 

 united below, so as to form a complete haemal arch. 



The Ethmoidal Sclerotome. — The ethmoidal sclerotome, 

 and the presphenoidal immediately behind it, present, in the 

 different forms of vertebrata, various remarkable modifications 

 of their elements, partly dependent on the position of the 

 olfactory lobes of the brain, partly on the position of the 

 olfactory capsules themselves, partly on peculiar adjustments 

 of the nasal fossae, and on the arrangements subservient to 

 mastication. 



The withdrawal from behind forwards of the neural axis, 

 in the course of development, from the posterior extremity of 

 the neural canal, is accompanied by well-known changes in 

 the evacuated but rapidly-increasing posterior trunk sclero- 



