184 Mary Isabella Steele 



ically can be found in great abundance. But at no time are 

 mitotic divisions seen. In a careful examination of a large num- 

 ber of sections only one cell has been found that suggested the 

 possibility of its being in mitotic division. The appearance of 

 this one suggests a late anaphase or an early telephase. Conse- 

 quently it is not certain that this is mitotic division. This nucleus 

 appears near the left edge of Fig. 53 at K. In any case it must be 

 admitted that amitosis is the regular method of cell division in 

 regenerating eyes of the forms studied, since in every specimen 

 examined during the stages of cell divisions amitosis has been 

 observed and mitosis has not been seen. 



That such is the case is somewhat unexpected since Miss Reed 

 ('04) found mitotic division abundant in the regenerating leg of a 

 crayfish. Miss Reed, however, observed that there were no 

 mitotic figures during the early stages of regeneration, although 

 new cells were being rapidly formed. Perhaps we may infer from 

 this that amitosis took place in the regenerating leg of the crayfish 

 during the preparatory stages at least. But one would hardly 

 expect such differences in cell division in forms so closely related 

 for example as crayfish and Palaemonetes. No observations have 

 been made upon histogenesis in the regenerating appendages of 

 hermit crabs, Palaemonetes or Crangon. Hence it cannot be 

 said whether or not the eye furnishes an unique exception to the 

 regeneration of other parts in these forms. 



Recently, however, many have come to regard amitosis as a 

 phenomenon of more frequent occurrence than has been generally 

 supposed. Meves ('91 and '94), McGregor ('99), Child ('04 and 

 '07), all describe amitosis as a normal phenomenon and con- 

 sequently no longer accept Vom Rath's view that a cell is nearing 

 its final dissolution when it begins to divide amitotically. 



On the other hand many of the more conservative investigators 

 are unwilling to admit that amitosis occurs as a normal phenom- 

 enon and believe that the apparent cases of amitosis can be 

 explained on some other grounds. But in all the instances hitherto 

 described amitosis has been found occurring along with mitosis. 

 In the present case, however, all of the cell divisions are amitotic 

 and they all take place in cells derived from the hypodermis; in 



