1 86 Mary Isahelle Steele 



of the individual and perhaps other factors not so apparent. 

 Besides individual differences displayed between members of the 

 same species there also appeared to be differences in the ability to 

 regenerate and the rate of regeneration among the three species 

 chiefly used, these differences being much more marked in the 

 regeneration of an eye than in the regeneration of an appendage. 

 The hermit crabs seem to completely regenerate an eye in shorter 

 time than either Palaemonetes or Crangon. But the final results 

 v^ere similar in all three forms. The fev^ significant differences 

 M^ill be pointed out and discussed later. 



I Entire Preparations of Regenerating Eyes 



A careful examination of the regenerating eye frequently reveals 

 a number of important features and is absolutely essential to the 

 later interpretation of the sections. Therefore outline surface 

 drawings have been made of all eyes later sectioned. In most 

 cases the normal eye was drawn in connection with the regener- 

 ating eye for comparison as to size, shape, etc. Frequently the 

 two eyes were sectioned together. These surface views which 

 had better be regarded as optical sections were drawn with a 

 camera after the eyes had been brought into oil preparatory to 

 embedding. Figs, i to 25 represent various stages of regenerating 

 eyes. 



Fig. I shows dorsal and ventral views of a Palaemonetes' eye 

 seven days after an operation which removed the ventral corneal 

 surface and immediately after a moult. A comparison of the 

 dorsal and ventral views shows that the injury is confined chiefly 

 to the underside. In shape the eye is practically normal. It is 

 not even flattened on the underside as the thinning out of the 

 pigment near the center would seem to indicate. As is usually 

 the case the injured eye is much smaller than the uninjured one. 

 Not only the region operated upon but the whole eye decreases in 

 size after the operation. This indicates that however localized 

 the operation may be the effect is much more extended. In this 

 particular case the part of the eye proximal to the injury measures 

 only three-fourths of the length of the same region in the unin- 

 jured eye. 



