PARKER: OPTIC CHIASMA IN TELEOSTS. 225 
ference being never more than ten per cent, and that in the remaining 
‘four (Menidia, Pomatomus, Tautogolabrus, and Gadus) this difference 
does not exceed in any instance twenty per cent. The differences, more- 
over, are not all in favor of one side ; in four species the excess is in left 
nerves dorsal, and in six in right nerves. Summing all together, it 
appears that in a total of one thousand the right nerve was dorsal 514 
times, the left 486. Since in each of the ten species both conditions 
are so abundantly represented and are often so nearly equal, one is 
justified in concluding that neither nerve is characteristically dorsal, 
TABLE I. 
Left optic 
nerve dorsal. 
Right optic 
nerve dorsal. 
1 Fundulus majalis (Walbaum). Woods Hole, Mass. . 
1 Menidia notata (Mitchill). Martha’s Vineyard, Mass. . 
Rhombus triacanthus (Peck). Boston Markets 
Pomatomus saltatrix (Linnaeus). Boston Markets . 
1Stenotomus chrysops (Linnaeus). Woods Hole, Mass. 
1 Tautogolabrus adspersus (Walbaum). Woods Hole, Mass. . 
1 Tautoga onitis (Linnaeus). Martha’s Vineyard, Mass. 
1 Prionotus carolinus (Linnaeus). Woods Hole, Mass. 
Gadus morrhua Linnaeus. Boston Markets aan 
Melanogrammus aeglefinus (Linnaeus). Boston Markets . 
Total 
though there is a slight difference in favor of the right. This difference 
is so slight, however, that it is probable that a larger number of observa- 
tions would give a still closer agreement in numbers, a state indicative 
of the unimportance from a physiological standpoint of the dorsal or the 
ventral position of a nerve at the chiasma.? 
Sincee both types of nerve crossing were abundantly represented in 
1 Material supplied from the Biological Laboratory of the United States Fish 
Commission, Woods Hole, Mass. 
2 A condition of approximate equality, essentially like that just pointed out, 
has been observed by F. H. Herrick (96, p. 148) in the right or left occurrence of 
the crushing claw of the common lobster and by Yerkes (:01, p. 424) in the enlarged 
claw of the male fiddler crab. 
