DEVELOPMENT OF THE CALIEORNIAN HAG-FISH. 277 



paired sense-orgaus, of gill-slits, and of nearly the adult 

 number of somites. 



IV. The brain portion of the early neural tube is of very 

 great length, one filth the entire length of the nerve-tube 

 (one quarter if tlie foldings in the brain wall be taken into 

 account), at a stage when nearly the adult number of somites 

 are present. It is to be inferred, therefore, that the craniote 

 brain is composed of a far longer region of the anterior neural 

 tract than has hitherto been supposed. It is thus probably 

 homologous with the branchial region of the cord, as well as 

 with the so-called brain of Amphioxus. 



V. The numerous foldings (asymmetrical) of the brain wall, 

 by which the regions come to appear, indicate a primitive 

 condition of the craniote brain, i. e. that the latter was 

 originally a tube of many vesicles^ (eight of these at least 

 between cerebellum and thalamus), which in the ontogeny of 

 higher forms have become merged into fewer and larger ones. 



VI. There is an almost entire absence of cranial flexure. 



VII. Although the developmental type of Bdellostoma is 

 distinctly meroblastic, it is noteworthy that there appears no 

 trace of a germ ring ; except in the immediate region of the 

 tail, the somites arise in situ at the sides of the neural axis. 



VIII. The early appearance in each segment of pronephric 

 tubules, similar to each other in essential characters, demon- 

 strates, as Price has shown, that the entire excretory system of 

 Myxinoids must, from the standpoint of ontogeny, be regarded 

 as univalent. If we accept, therefore, SpengePs criticisms of 

 the results of Semon on the morphology of the excretory 

 system in Myxine, we must nevertheless admit Semon's a 

 priori view as to its homology as a pronephros. 



Note on the above by J. T. Cunningham, M. A. — It is, 

 I think, of some interest that the method of fishing by which 

 alone eggs of a Myxinoid have been obtained in California is 



^ The writer believes that these may be distinguished from the neuromeres 

 of Locy and receut authors, which are not disliuctly vesicular, and which 

 accur in cord as well as iu braiu. 



