20 BRITISH PARASITIC COPEPODA. 



four pairs of feet at the anterior end of the narrow 

 neck. The feet are exactly as they exist in the fully 

 developed cyclops stage, both in size and structure. 

 The protopodite is two-jointed. The exopodite of the 

 whole four pairs is two-jointed. The endopodite of 

 the first two pairs is also two-jointed. The third and 

 fourth pairs of feet have no endopodite. 



The external openings are the mouth placed at the 

 apex of the head, the openings of the oviducts on the 

 ventral aspect of the S-shaped region, and the anus at 

 the blunt apex of the abdomen. 



The colour of the living animal is a dark red, due 

 to the contained blood. When removed from the fish 

 and placed in sea-water the colour disappears. Speci- 

 mens of Lernsea removed from their host and placed 

 in sea- water do not appear to live longer than twelve 

 hours. The parasites are simply inert sacs quite in- 

 capable of movement. Occasionally they are covered 

 with colonies of hydroids which may entirely obscure 

 them. The exoskeleton consists of chitinous cuticle 

 moderately thin and soft in the swollen part, but thick 

 and hard on the neck and head. 



The mouth of the adult opens directly into the 

 alimentary canal. The oesophagus and true stomach 

 have entirely disappeared during the metamorphoses 

 of the cephalo-thorax. A peristaltic movement of the 

 intestine similar to that of Lepeopktiievnts can be seen 

 in the living animal. There are no indications of 

 digestive glands, and it is probable that the digestion 

 is intracellular. 



There is no heart in adult Lernsea and no move- 

 ment of fluids that would indicate a blood-circulation. 

 The animal is probably dependent on the blood sucked 

 from the host for the oxygen necessary to maintain 



