239 
tions. In the calculations fractions of less value than one-half were 
dropped and those of a value of one-half or more were called one. It will 
be observed from the groups described—and the same is true of the other 
groups—that when the number of scales is the same on each side or not 
more than a difference of one, the actual column exceeds the calculated, 
and as the difference increases, the calculated column exceeds the actual. 
A comparison of the corresponding groups in the two columns in every 
case gives the same results ds in those described, all of which demon- 
strates the tendency to bilateral symmetry or a marked correlation in the 
variation of the two sides. 
Pretiminary Note Upon THE ARRANGEMENT OF Rops AND CONES IN THE 
Retina oF FisHres. By C. H. EIGENMANN AND GEORGE HANSELL. 
(Abstract.] 
A yariety of fish eyes were examined, and it was found that in most 
cases the rods and cones are arranged in a regular pattern. This pattern 
is either that described by Hannover and Ryder for fishes or a slight 
modification of this pattern. 
DEGENERATION IN THE EYES OF THE AMBLYOPSIDH, ITs PLAN, PROCESS AND 
Causes. By Cari H. EIGENMANN. 
(Summary only.] 
1. There are at least six species of ‘‘blind fishes,” Amblyopside, inhabiting 
North America, three with well-developed eyes and three with mere vestiges. 
2. The three species with vestigial eyes are descended from generically dis- 
tinct ancestors with well-developed eyes. 
3. These species can be more readily distinguished by the structure of their 
eyes than by any other characteristic. 
4. The most highly-developed eye is much smaller and simpler than the eye 
of normal-eyed fishes. 
5. The structure of their eyes may be represented by the following key to 
the genera and species. 
a. Vitreous body and lens normal,.the eye functional. No scleral carti- 
lages. Eye permanently connected with the brain by the optic nerve. Eye 
muscles normal. No optic fibre layer. Minimum diameter of the eye .700 yu. 
~ 
Chologaster. 
