238 Mary IsaheUe Steele 



In some cases not even a vestige of the eye remained; in others, 

 stumps of considerable length persisted. But in no cases where 

 the split extended into the optic ganglion was there any sign of 

 regeneration. 



Figs. 16 and 22 represent instances in one of which an eye 

 regenerated and in the other there were no signs of a regenerating 

 eye. The specimen from which Fig. 16 was taken lived sixty- five 

 days after the eye was split. The regenerated eye is about six- 

 sevenths of the length of the normal eye. Sections show that new 

 ommatidia have regenerated. The eye is not altogether normal 

 in structure, however. The eye stump shown in Fig. 22 was 

 taken from an individual that lived seventeen days after the 

 operation. Apparently the entire optic ganglion has degenerated. 

 There are no definite indications of regeneration. The stump of 

 the optic nerve tapers to a point, perhaps indicating that degener- 

 ation is still incomplete. The stump is little more than one-third 

 the length of normal eye. 



No additional facts of importance were gained from the experi- 

 ment of splitting the eye. These results obtained serve chiefly as 

 additional proof that an injury to any part of the eye is followed by 

 widespread degeneration of the tissues and that in the case of 

 Palaemonetes, after an injury to the optic ganglion usually no 

 regeneration takes place. 



Summary 



In summing up the results of the experiments discussed in this 

 paper the following points are to be noted : 



1 The death of the animal which so frequently follows imme- 

 diately upon the operation is perhaps due rather to its eflPect upon 

 the nervous system than to loss of blood. 



2 The healing of the wound takes place by the formation of a 

 provisional crust over the cut surface and later by the development 

 of a new cuticle beneath this crust. 



a The crust is formed of hypodermal cells and a chitinous 

 secretion. Intermingled with this are blood cells and the cells of 

 the injured tissues. From two to three days are required for the 

 formation of the crust. 



