DEVELOPMENT AND LIFE HISTORY OF SOME TELEOSTS 
639 
developed in the vertical fins. A slight depression is evident above the right eye 
through which the left eye is destined to migrate, as illustrated in the older fish shown 
in figure 158. However, at this stage the eyes remain symmetrically placed. The fish 
still swam upright in deep water, but on a hollowed microscope slide containing insuffi- 
cient water to “float” them vertically, they invaribly swam or rested on the left side. 
Young fish 82 days old . — The specimen illustrated in figure 157, which is 32 days 
old and 3.0 mm long, after preservation, has the depression over the right eye, described 
for the fish 26 days old, more pronounced. The second line shown in the drawing is 
the actual outline of the interorbital, for above it is only a transparent membrane. 
However, the eyes remain symmetrically placed on the opposite sides of the head. 
Note in the illustration that the pigment blotches on the dorsal and anal fins remain 
placed essentially as in the early larvae. 
Young fish 34 days old . — The fish illustrated in figure 158 is 34 days old. There- 
fore, only 2 days older than the one shown in figure 157. However, this fish is larger, 
being 5.0 mm long after preservation, and it is much advanced in development. Note 
in the illustration that the left eye has just entered the depression in the forehead. 
At this size the mouth already is much twisted, essentially as in the adult. Ventral 
fins now are developed. Note also that the pectoral fin membranes persist. It seems 
significant, however, that in contrast with the other fins no definite rays have devel- 
oped. It is, furthermore, noteworthy that the pigment spots on the dorsal and anal 
fin s persist essentially as in the early larvae. No loss of pigmentation on the blind 
side has taken place. 
Although one fish lived in the aquarium to reach the age of 41 days, development 
had not proceeded as far as in the specimen 34 days old, just described. As the smallest 
specimen taken in nature is 18 mm long, and essentially a young adult, an unfilled 
gap in the development remains between this specimen and the 5.0-mm one, described 
in the foregoing paragraph. 
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