A HISTORY OF WORCESTERSHIRE 



is still a chance that where the foe exists there also the victim may be 

 found. 



Of the Branchiura the single British species, Argulus foliaceus 

 (Linn.), parasitic on carp and trout and sticklebacks and some other 

 fishes, is likely to be met with wherever its hosts are systematically 

 searched for its discovery. It is easily recognized by its disk-like form 

 and the pair of suckers which represent the second maxillas. 



Among parasites, which offer so rich a field for minute research, 

 two others may be mentioned as with little doubt occurring in Wor- 

 cestershire. These are the Copepoda, Achtheres percarum^ von Nord- 

 mann, and hernceopoda salmonea (Linn.). They agree in having one of 

 their pairs of jaws, the maxillipeds, modified for attachment to the body 

 of the fish they infest. As the specific names indicate, the former 

 species devotes itself to the perch, while the other gives a preference to 

 the salmon. The salmon, with its change of residence from salt water 

 to fresh, has the interesting privilege of changing its parasites, the 

 marine Copepoda forsaking it after it has left the sea, and giving place 

 to the freshwater Lernceopoda. But I have the authority of Mr. J. W. 

 Willis-Bund, F.L.S., of Wick Episcopi, Worcester, for including in the 

 fauna of the county the seafaring parasite which is found on the clean- 

 run salmon. The creature in question is named Lepeophtheirus stromii, 

 Baird. It is much less abnormal than the form with which it is wont 

 to change places, but still adaptation to life on the slippery body of a 

 fish has made it in some respects unlike the free-swimming members of 

 its order. It has a flattened appearance, the front division broadly oval, 

 the tail part long and narrow, but not nearly so long as the parts which 

 are frequently supposed to be its tail, namely, the two slender ovisacs, 

 or egg-bearing tubes, which are three or four times as long as the body. 

 The male is much smaller than the female. Mr. Willis-Bund has also 

 observed parasites on trout and on some of the Cyprinids. Of the latter 

 the carp is known to entertain Ergasilus sieboldii, von Nordmann, and 

 other members of the family support other Copepoda of various eccentric 

 shapes. 



On the whole, then, it will be understood that if observed facts are 

 rather meagre for a carcinological history of Worcestershire, there are 

 very considerable natural opportunities for its future development. 



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