THE ECONOMIC RELATIONS, ANATOMY, AND LIFE HISTORY 

 OF THE GENUS LERNAEA. 



By CHARLES BRANCH WILSON, Ph. D., 



Stale Normal School, Department of Biology, Weslfield, Mass. 



Contribution from the United States Fisheries Biological Station, Fairport, Iowa. 



INTRODUCTORY. 



During the summer of 1914 while working at the Bureau of Fisheries station at 

 Fairport, Iowa, many new species of copepods parasitic upon fresh-water fish were 

 obtained, and interesting bionomic relations between these parasites and mussel glochidia 

 were discovered. The results of these investigations have already been published." 



Among the new species was one belonging to the genus Lerncea, which proved to 

 be of exceptional interest, since larvae were foimd in various stages of development. 

 But not enough were obtained to give anything like a complete life history, and conse- 

 quently this was left until the following summer, 1915. At that time additional larval 

 stages were found and the entire development was carried up to the adult form. 



Two new species were discovered and those already described were carefully re- 

 viewed, so that the entire genus might be placed upon a sound and substantial basis. 

 Specimens of the adults of various species were sectioned and the entire internal anatomy 

 was reconsidered, together with the oogenesis, in the light of the series thus obtained. 

 And it is vastly to the credit of those old observers that all the wonderful advance in 

 technique since their day has only been able to supplement, and not to supplant, their 

 painstaking work. The larvae were also sectioned and their anatomy was fully worked 

 out. 



Material was thus provided for both the external and internal morphology of the 

 larva as well as the adult, for much of the histology, and for the entire hfe history, all 

 of which have been incorporated in the present paper. 



This work, especially the life history, is one of the most important factors in deter- 

 mining the systematic position of the genus, which ought now to be fairly well 

 established. 



With the two new species here presented the number now recognized in the genus 

 reaches 17, more than half of which are American. 



o Bulletin, Bureau of Fisheries, vol. 34. 1914. p. 331-374, pi. 60-74. 



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