THE EYE OF THE PARASITIC COPEPOD, SALMINCOLA 



EDWARDSII OLSSON (LERN^EOPODA 



EDWARDSII OLSSON). 



NATHAN FASTEN, 



DEPARTMENT OF ZOOLOGY, UNIVERSITY OF 

 WASHINGTON, SEATTLE. 



CONTENTS. 

 Introductory Remarks 407 



Methods 408 



Gross Structure of the Eye 409 



Internal Structure of the Eye 410 



Summary 411 



Bibliography 412 



INTRODUCTORY REMARKS. 



The material from which the following studies were made 

 consisted of numerous free-living larvae of Salmincola edwardsii 

 (LerncBOpoda edwardsii) Olsson, a parasitic copepod of the family 

 Lernseopodidae, which infests the common brook-trout, Sahelinus 

 fontinalis. In three former papers (Fasten '12, '13, '14) the 

 author has discussed the economic importance, the behavior and 

 the fertilization process of the parasite. In this publication, 

 the structure of the eye will be described. 



Wilson (1911) in his paper on the development of Achtheres 

 amUoplitis Kellicott, one of the Lernaeopodidae observes that the 

 eye is rudimentary in character and is only developed during 

 the metanauplius stage, while the organism is still surrounded 

 by its embryonic membranes. Wilson says, "the extremely 

 rudimentary eye (e) can now be distinguished inside the coils of 

 the attachment filament. It is made up of three ovate ocelli, 

 two dorso-lateral and one inferomedian, which are entirely sepa- 

 rated from one another and devoid of pigment. The structure 

 of each ocellus has also degenerated until all that remains is a 

 more or less granular mass, staining deeply in haematoxylin and 

 containing near its anterior end three lighter spots. No trace 

 of lenses can be found in any of the sections and the entire 



407 



