Eyes of Molluscs and Arthropods. 



By 



William Patteu, 



from Boston, U. S. America. 



With Piate 28—32. 



lutroduction, 



The followiug studies were beguu at tlie Zoological Station in 

 Naples late iu the Spring- of 1885, and were coutinued with several in- 

 terruptions until the foUowing Janiiary. 



It is difficult to express my gratitude to the Director and Assistants 

 of the Zoological Station for the personal kindness shown towards me ; 

 to do it in words would sound extravagant to those who did not under- 

 stand the peculiar circiimstances. It is with mingled feelings of hum- 

 iliation and admiration, that I coutrast the uneertain and hesitating 

 Support given by Americans to such a purely scientific under- 

 taking, with the frank and generous manner in which Americans have 

 been invariably treated by the Director of this institution. Whatever 

 may be the reasons, or apologies that could be offered for such a con- 

 dition, I sincerely hope and trust it will not remain so long. 



It was my Intention, originally, to study the anatomy and develop- 

 ment of the eye of Pecten, hoping to find some explanation for the 

 presence of such a large number of highly developed eyes — if indeed 

 they were such — in an animai which. apparently, could make no special 

 use of them. 



Accepting the modern theories of evolutiou, we are brought to a 

 Stand-still in attempting to apply this method of reasoning to the ori- 

 gin of the eyes of Pecten. There can be no doubt that structurally. 

 they are as perfectly adapted for seeing as those of the Cephalopods. 

 But while two eyes are sufticient for the latter animals. Pecten, whose 



