SEA-FISHERIES LABORATORY. 193 



examination it is possible to collect a series of these 

 parasites, from the early " chalimus " stage to the adult 

 condition, from one fish. Sometimes only a few speci- 

 mens occur on the fish. At other times large numbers 

 are to be found. It is by no means rare to find between 

 twenty and thirty mature females under each pectoral 

 fin alone, as in the case which is illustrated in the cut. One 

 hundred specimens of another species, L. hippoglossi, have 

 been collected from the " white " side of a halibut in the 

 Aberdeen Fish Market. The average length of a mature 



Lepeophtheirus pectoralis, 32 specimens, on the pectoral fin of a Flounder, 

 from a photograph. 



egg-bearing female is one-fifth of an inch, and of a male 

 one-ninth of an inch. A mature female measures about 

 one-tenth of an inch at its greatest breadth, and a male 

 one-twelfth of an inch. These parasites attach themselves 

 to the fish by means of their powerful second maxillipedes, 

 assisted by the antenna?, and a decided pull has to be 

 exerted before they can be torn away. By depressing 

 the edges of the carapace and applying them closely to 

 the skin, the parasite can increase its holding power to 

 3uch an extent that the posterior end can be torn from the 



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