482 Suborder Hete-rosomata 



generally, the process takes place at an earlier stage than in 

 Plato phrys. 



Optic Nerves of Flounders. In the Bulletin of the Museum of 

 Comparative Zoology (Vol. XL, No. 5) Professor George H. 

 Parker discusses the relations of the optic nerves in the group 

 of flounders or flatfishes. 



In the bony fishes the optic nerves pass to the optic lobes 

 of the brain, the one passing to the lobes of the opposite side 

 simply lying over the other, without intermingling of fibers, 

 such as takes' place in the higher vertebrates and in the more 

 primitive fishes. 



According to Parker's observations, in ordinary bony fishes 

 the right nerve may be indifferently above or below the other. 

 In 1000 specimens of ten common species, 486 have the left 

 nerve uppermost and 514 the right nerve. In most individual 

 species the numbers are practically equal. Thus, in the had- 

 dock, 48 have the left nerve uppermost and 52 the right nerve. 



In the unsymmetrical teleosts or flounders, and soles, this 

 condition no longer obtains. In those species of flounder with 

 the eyes on the right side 236 individuals, representing sixteen 

 species, had the left nerve uppermost in all cases. 



Of flounders with the eyes on the left side, 131 individuals, 

 representing nine species, all have the right nerve uppermost. 



There are a few species of flounders in which reversed 

 examples are so common that the species may be described 



as having the eyes on the right 



^"!^^ or left side indifferently. In all 



'-*"-" * 



-* these species, however, whether 

 FIG. 427. Young Flounder, just dextral or sinistral, the relation 



hatched, with symmetrical eyes. n f t ^ p ripfvp<; conforms tn flip 

 (After S. R. Williams.) 



type and is not influenced by 



the individual deviation. Thus the starry flounder (Platich- 

 thys] belongs to the dextral group. In 50 normal specimens, 

 the eyes on the right have the left nerve dorsal, while the 

 left nerve is also uppermost in 50 reversed examples with eyes 

 on the left. In 15 examples of the California bastard halibut 

 (Paralichthys calif ornicus} , normally sinistral, the right eye is 

 always uppermost. It is uppermost in n reversed examples. 

 Among the soles this uniformity or monomorphism no 



