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
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