STUDIES ON THE EYES OF ARTHROPODS. 



WILLIAM PATTEN, PH.D. 



1. Development of the Eyes of Vespa, with Obser- 

 vations on the Ocelli of some Insects. 



In a former paper (27) I gave an account of some observa- 

 tions on the structure of the compound eyes of Arthropods. 

 Those observations, which were made almost entirely upon 

 adult eyes, differed widely from those of recent writers on this 

 subject. I desired to confirm, by embryological data, my obser- 

 vations on the continuity of the so-called rhabdom with the 

 crystalline-cone cells, and on the nature of the comeagen} It 

 was also important to determine whether there was any simi- 

 larity between the development of the compound eyes and the 

 ocelli. Moreover, if the opinion expressed in my former paper, 

 that the primitive Arthropod eye was an invaginated and closed 

 vesicle, be tenable, then it is necessary to show that the simplest 

 Arthropod ocelli, which have heretofore been regarded as simple 

 cup-like pits, are in reality closed vesicles. It is also neces- 

 sary, in order to maintain my views on the origin of the com- 



' The term " corneal hypodermis " employed in the paper referred to above is 

 unsatisfactory on account of its length. In this paper I shall substitute corneagen for 

 corneal hypodermis. 



Postscript. — Dr. Mark's memoir on " Simple Eyes in Arthropods," was 

 received as this paper was going to the printer. He suggests " lentigen " to desig- 

 nate the layer of cells called by me corneagen. There are some considerations which 

 make the word " lentigen " preferable to " corneagen ; " but it seems to me they do not 

 outweigh the objections which might be urged against it. It is important that the 

 term be applicable to the layer of cells in question throughout the Arthropods at 

 least. But there are numerous instances in which this layer is undoubtedly present, 

 although no lenses are formed by it : Branchipus, Pkronima, and Ganunay-us, etc. 

 On the other hand in Peripatus a lens is present, although it is not secreted bv that 

 layer of cells which, on morphological grounds, should be called lentigen, provided 

 Dr. Mark's nomenclature were adopted. 



