68 MR WILLIAM TURNER AND DR H. S. WILSON ON THE 



description of the parasite. The most lengthened account of the animal, which 

 comprises a description of the male and female, and for the first time, of the 

 larval form, has been recently given by Claus.* 



As there are various discrepancies of statement in the descriptions of the 

 above authors, and as we have been able more fully to elucidate several points in 

 the anatomy of the animal, we have been induced to place an account of it before 

 the Society. Owing to the diverse forms presented by the female, the male, and 

 the larva, it will be necessary to consider them under separate heads. 



Female. — Average length of body fths to \ inch, greatest breadth, |th of inch. 

 Body elongated, capable of division into a cephalic, thoracic and abdominal part. 

 Ventral surface concave. Dorsal surface convex, especially when the animal is 

 irritated during life, when it throws its back into a highly arched form. 



Cephalic part about ^th the size of thoracic. Length and breadth nearly 

 equal. Like the other divisions of the body, it has a perfect bilaterality. On 

 each lateral half of the dorsal surface of the head is a chitinic plate, which, 

 reaching inwards to the dorsal mesial line, forms, by apposition of its margin to 

 that of its fellow, a well-marked chitinic rod, which extends as far as the anterior 

 margin of the head. From each side of the head a short process projects back- 

 wards and outwards. 



To the anterior margin of the head two well-marked processes, or antennae, 

 are connected (fig, 1, 2, 5, a). Each arises immediately on one side of the 

 middle line by a constricted peduncle, beyond which the antenna expands into 

 a much broader portion, flat on the dorsal, convex on the ventral aspect, which 

 passes outwards, and then, diminishing considerably in size, bends slightly back- 

 wards, and terminates in a bluntly conical extremity. The antenna presents, 

 towards its free end, two slightly marked constrictions, which would appear to 

 indicate its division into three segments. Springing from the two distal seg- 

 ments are several stiff conical hairs, the central part of each of which may 

 be seen, through the transparent chitinic covering, to be continuous with the 

 parenchymatous substance of the antenna (fig. 3). It is possible that these 

 papilla-like hairs may serve the purpose of touch organs. Situated immediately 

 behind the antennae, and arising quite from the ventral aspect of the head, 

 are a pair of hook-like processes, which are important, because it is through 

 them that the parasite attaches itself to the branchial membrane of the fish 

 which it infests. Each hook possesses a very well defined, highly curved form, 

 the convexity being directed outwards, the point inwards (fig. 4, a, b). In 

 shape it represents a three-sided pyramid, with the angles rounded. It is 



* Ueber der Bau und die Entwickelung Parasitisclier Crustaceen, Cassel 1858. 

 Synonyms : — Chondracanthus Lophii, Johnston^, Rathke. Ckondr acanthus gibbosus, Kroter, 

 W. TnaMPSON, Van Beneden, Claus. Lernentoma Lophii, Baird. 



