INTRODUCTION. 21 



life. It is possible that the early death after removal 

 from the host is due to the inability to take up oxygen 

 from the water. 



The muscular system is represented by a network of 

 fibres between the integument and the alimentary canal. 



There does not appear to be any nervous system in 

 the adult. 



The reproductive organs of Lernaea, like those of 

 Lepeoplitlieirus, are bilaterally symmetrical, but during 

 the metamorphoses of the female the ovaries undergo 

 a great change of position. They are displaced from 

 the cephalo-thorax and pass into the genital segment, 

 where they occupy a narrow region at the apex of the 

 deep indentation. The two ovaries are practically 

 fused together. The oviducts arise from their anterior 

 ends, pass across the segment to its ventral surface, 

 and then course along each side of the median line to 

 the external openings. The cement-glands are nearly 

 of the same length and breadth as the oviducts and lie 

 underneath them. The posterior end communicates 

 with the oviduct just inside the opening to the 

 exterior. The ovisacs consist of long slender con- 

 voluted tubes which may reach the length of eight 

 inches when straightened out. The eggs are arranged 

 in a single column. The female is fertilized shortly 

 before the completion of the cyclops stage. It is 

 probable that the sperms pass up the oviduct and 

 fertilize the eggs very soon afterwards, as no trace of 

 a receptaculum seminis can be made out in the adult. 



The young Lernsea hatches as a nauplius with three 

 pairs of appendages similar to those of the Lepeo- 

 plitlieirus nauplii. It leads a short pelagic life and 

 then settles on the gill-filaments of the flounder and 

 plaice and occasionally other fishes. It attaches itself 



