REGENERATION IN FUNDULUS HETEROCLITUS. I/ 



the difficulty the fish experienced in grasping and holding its 

 food. 



SCALES. 



On June 20, 1906, the scales were removed from definite areas 

 of a number of fish. This operation was performed in such a 

 way as to injure as little as possible the underlying dermis, each 

 scale being separately pulled out with a pair of fine forceps. 

 Three sets of fifteen fish each were used in this experiment, each 

 set of fish having the scales removed from a different part of the 

 body. In three weeks time the new scales were coming in 

 rapidly, some of them being one third the normal size, though 

 very thin and soft. Two weeks later, the new scales were still 

 only one-half to three quarters the length of a fully grown scale, 

 though many were as broad. It appears then, that regenerating 

 scales grow faster in breadth than in length. At this period or 

 a little earlier the characteristic dotted pigment appears. At 

 first the dots are comparatively few in number but continue to 

 increase until the pigmentation, normal, for the position of the 

 scale is attained. Thus each scale, from whatever region it is 

 taken, is replaced by a new one pigmented exactly like the 

 original. The fish in this experiment were kept ten weeks in all 

 and at the end of that period the regenerated scales were prac- 

 tically normal in size, thickness and color though sometimes 

 slightly irregular in shape. 



LENS. 



On June 21, 1906, the lens was removed from one eye of 

 a number of fish. The operation was performed by slitting the 

 cornea with a sharp scalpel and then gently pressing the eyeball 

 with forceps until the lens popped out. In all thirty-six fish were 

 used which were divided into two sets of eighteen each. In one 

 of these sets the iris was slit in addition. These fish were kept 

 until August 29, about ten weeks, when eleven fish remained in 

 one set and nine in the other. When the lens is squeezed out 

 some of the vitreous humor goes with it and after the operation 

 the eyeball appears flattened. However the cornea heals over 

 very quickly and the eye soon assumes its regular contour, differ- 

 ing only from normal apparently, in a slight dilation of the pupil. 



