348 • Robert J. Terry. 



in support of the theory of the epiphysis of this teleost being an 

 ocular organ, either rudimentary or degenerate. Whatever may be 

 the significance of the syncytial network, its formation in Opsanus 

 goes hand in hand with the development of the epiphyseal cavity, 

 a. process analogous with that which produces the cavities of 

 the central nervous system in the teleosts. 



As to the fundamental question of the independence of origin 

 of the two epiphyseal vesicles, the evidence afforded by Hill's 

 material is not convincing. In Opsanus the two outgrowths 

 are entirely separate and there is no question of one of them being 

 developed from the other. The smaller bud appears later than 

 the definitive epiphysis and arises from the diencephalic roof. It 

 lies at first to the left and a little in advance of the main organ 

 but secondarily comes into connection with the superior commis- 

 sure and the post- velar arch. This forward migration recalls the 

 shifting of the anterior vesicle of Amia and Lacerta. 



The end of the epiphysis, from the time it is first seen in 

 Opsanus, is closely related with the overlying tissues. In the 

 smallest embryo the cranial mesenchyma extends between the 

 epiphysis and ectoderm. In larger embryos and in larvae, 

 strands of this tissue and finally connective tissue fibers pro- 

 ceed from the epiphysis to the roof of the cranium. There is 

 no evidence to show that the function of these connecting strands 

 is anything more than a passive one in fixing the epiphysis, but 

 the early appearance of a bond between the end-vesicle and the 

 overlying parts is suggestive of some other relation. Dean 

 '95) has expressed the opinion that the epiphysis of fishes is con- 

 nected with the innervation of the sensory canals of the head, at 

 the same time opposing the theory of its relation to a median eye. 

 In the present study attention was specially directed to a search 

 for evidence in support in this view, but there was nothing ob- 

 served which pointed to a relation between the epiphysis and the 

 lateral line system, beyond the fact that the former is at one time 

 directed toward the supraorbital commissural canal and is ap- 

 proximated rather closely to it. 



The forward inclination of the epiphysis, occurring at the time 

 when the roof of the cranium is first laid out in the mesenchyma. 



