172 Mary Isahelle Steele 



bearing a number of sensory hairs. (Fig. 37, o.sq.) And finally, 

 there are no accessory pigment cells in the hermit crab's eye. 

 These cells are very conspicuous in the eyes of Palaemonetes. 



IV The Preliminary Regenerative Process 



The preparatory stages leading to the regeneration of an eye 

 stump consist chiefly of the following processes; the healing of the 

 wound, the removal of the injured tissues and the active prolifera- 

 tion of new cells of a comparatively undifferentiated character. 

 In removing any part of the eye the injury to the remaining soft, 

 inner tissues is considerable. Especially is this true when the cut 

 passes through the ommatidial region. Much of the tissue sur- 

 rounding the wound is crushed and torn out of place. On this 

 account the process of healing over the cut surface is much more 

 difficult to follow than the healing of the wound after an antenna or 

 leg has been removed. 



Before taking up the description of the preliminary regenerative 

 process it will be perhaps of interest to give in brief the immediate 

 effects of the operation. The death of the animal which so fre- 

 quently follows close upon the operation seems often to be due 

 chiefly to nervous shock. It cannot be caused by loss of blood 

 alone for usually there is no profuse bleeding. When the eye of 

 Palaemonetes is operated upon the animal often turns over and 

 over .ten to forty times as soon as it is released and returned to the 

 water. Many of the animals die before they succeed in righting 

 themselves. Others lie upon their sides several hours after they 

 have ceased revolving and die without showing any normal activi- 

 ties or regaining their equilibrium. It very seldom happens that 

 animals which whirl over and over many times after the operation 

 ever recover from its immediate effects. These apparently help- 

 less motions indicate that the operation has caused the loss of 

 equilibrium. 



Crayfish sometimes exhibit these uncontrolled whirling move- 

 ments. Similar movements are also noted in fresh-water Gam- 

 marus and in Ascellus. In Gammarus and Ascellus these move- 

 ments are executed after the removal of the antennae or some of 



