PHYSIOGENESIS. 243 



young and somewhat larger than in the adult. We 

 quote and translate from Zeller's account : 



" l The development of the eyes is very remarkable ; 

 they are immediately perceived and present themselves 

 as small, but entirely black and clearly drawn circular 

 points, with a slit which is very narrow, and yet, at 

 the same time, well defined, and which penetrates 

 from the lower circumference out to the middle. 



"'Indeed, one can hardly doubt that this astonish- 

 ing development of the eye has been accomplished by 

 the influence of light, as has also the pigmentation of 

 the skin, the reddish-white ground-color of which ap- 

 pears thickly studded with very small brownish- gray 

 points mixed with detached white ones, over the upper 

 surface of the head and over the back, down over the 

 sides of the yellowish abdomen. Even on the edge of 

 the fins (Floss ens auni) the pigment is found. On the 

 other hand, there is a whitish spot over the snout, as 

 is likewise the case in the adult creatures which have 

 been colored by the light. Both the under surface of 

 the head and the entire abdomen are shown free from 

 pigment like the limbs. . . . 



'"I cannot specify very exactly as to when the pig- 

 mentation of the skin begins, but, in any case, it is 

 very early, and often earlier that the first beginning of 

 the eyes can be discovered. The latter occurs toward 

 the end of the twelfth week, at which time a thin, light 

 gray line, which still appears overgrown, may be per- 

 ceived, forming a half-circle, open underneath. Then 

 while this line subsequently becomes clearer and 

 darker, and its ends grow further under and towards 

 each other, there also takes place simultaneously a 

 progression of the pigment larger towards the middle 

 point, and the circle finally seems closed and filled up 



