232 Mary Isahelle Steele 



there is evidence that in some cases hermit crabs regenerate an 

 antenna-hke appendage when part of the ganghon has been left in 

 the eye stalk. We have then the following conditions for hermit 

 crabs at least. First, when the cut comes at a level which leaves 

 as much as two sections of the optic ganglion intact an eye may 

 regenerate {a-b, text Fig. 2). Second, w^hen the cut is made at the 

 base or slightly above the base of the eye stalk'(c-J, text Fig. 2) so 

 that little or none of the optic ganglion remains the regeneration 

 of an antenna-like appendage is possible. Lastly, if the eye is 

 removed at a level intermediate between a-b and c-d (text Fig. 2) 

 no regeneration follows. 



Text Fig. 2 The line a-h represents approximately the level from which a hermit crab may regen- 

 erate an eye. From the level of the line c-d or below it a heteromorphic appendage may regenerate. 

 No regeneration takes place from intermediate level, e.g., from the level e-j. 



It is possible, perhaps even probable, that the character of the 

 hypodermis differs more or less at these different levels. It is 

 even conceivable that the hypodermis should be capable of one 

 sort of regeneration at the level a-b or above it, and of another 

 sort at the level c-d or below it; but there is certainly no apparent 

 reason why no regeneration whatever should take place if the eye 

 is removed at a plane intermediate between these two levels. So 

 far as careful microscopic examination can determine there is no 

 difference in the hypodermal cells underlying the cuticle proximal 



