lighted to find some of these objects thickly beset in places 

 by the larvae for w}:ich I was looking. I was still more de- 

 lighted wher: in one of the largest of tliese larvae I noticed | 

 certain glistening spots in the bases of the tentacles ana 

 found on exar.iining them with a microscope that these spots 

 were, as I suspected, unmistakably masses of crystals that 

 would form parts of future marginal sense organs. After this 



discovery, I entered, with the advice of Professor : rooks, in- 



t 

 to an investigation of this i'laterial, th'. results of which are 



embodied in the present paper. I wish to express my thanks 

 to him for his lielp and encourci^'jom.cnt during this work and I 

 am also indebted to him for su£';^jesting the na,me by which I 

 propose to call this species. Tt is derived, from Xam.acha, . 

 which was the name used by the Aborigines for the island that 

 we now know as Jamaica. 



A single "lonstrcus specimen with but two subgenital cavi- 

 ties, with extraordinarily large oral vesicles, and otherwise 

 misshapen, that perhaps belongs to this species, was found in 

 the harbor near "ort Poyal . Except for this doubtful specimen 

 the only locality in which this species has 'neen found is the 

 lagoon that I have described. Although the adults and the 

 young in nearly all stages were present at this place in such 



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