PARKER: OPTIC CHIASMA IN TELEOSTS. yo | 
sinistral specimen, and Pleuronectes flesus, also dextral, has been re- 
ported by the same authority (:00, p. 339) as represented in different 
localities by from five to thirty-six per cent of sinistral individuals. In 
American waters three such species are known: the halibut of the 
Atlantic and Pacific coasts, and the bastard halibut and starry flounder 
of the California coast. The halibut is typically a dextral species and, 
like Pleuronectes platessa, is only rarely represented by sinistral in- 
dividuals. The bastard halibut, according to Jordan and Evermann 
(96-00, p. 2625), is almost as frequently dextral as sinistral, and the 
starry flounder, a dextral species, is said by the same authorities 
TABLE IV. 
Sinistral Dextral 
Faminy PLEURONECTIDAE. individuals. individuals. 
Subfamily Hippoglossinae. 
Left nerve 
dorsal. 
Right nerve 
dorsal. 
Left nerve 
dorsal. 
Right nerve 
dorsal. 
Halibut, Hippoglossus hippoglossus (Linnaeus). 
Grand Banks Ee A 
2Bastard halibut, Paralichthys  californicus 
(Ayres). San Francisco Markets 
Subfamily Pleuronectinae. 
2 Starry flounder, Platichthys stellatus (Pallas). 
San Francisco Markets a 
(96-00, p. 2607) to be frequently sinistral. If now the determina- 
tions as to which optic nerve shall be dorsal at the chiasma and as to 
which eye shall subsequently migrate are dependent phenomena, it 
follows that in those species in which the left eye migrates in some 
individuals and the right one in others, there should be found two 
corresponding types of nerve crossings. In ascertaining whether such 
is the case or not, [ examined specimens of the three American species 
mentioned ; the results of this examination are given in Table IV. 
1 Atypical individuals are indicated by italic numerals. 
2 Material supplied in part by the United States Commission of Fish and 
Fisheries. 
