SEA-FISHERIES LABORATORY. 227 



a high power, they are found to be subspherical, granular, 

 and of various shades of greenish yellow colour. Some 

 of the cells exhibit faint amoeboid movement. It is pro- 

 bable, therefore, that the digestion is intracellular. 



The food of these parasites is undoubtedly blood which 

 we find in the alimentary canal, but whether the absence 

 of digestive glands in the adult accounts for its unchanged 

 appearance has not been ascertained. In the young, 

 where there is an apparent digestive gland, the contents 

 of the alimentary canal are not red. 



Circulation and Respiration. 



There is no heart or vascular system, and in the adult 

 no movement of fluids could be observed which would 

 indicate a blood circulation. The animal is probably 

 dependent upon the blood sucked from its host for the 

 supply of oxygen necessary to maintain life. It is there- 

 fore possible that the early death after removal from the 

 fish is due largely to the inability to take up oxygen from 

 the water. The blood circulation could not be satisfac- 

 torily traced in the cyclops stage. 



The Muscular System. 



The muscular system in the cyclops stage, although not 

 so highly developed, is practically similar to that of 

 Lepeophtheirus. In the adult female it is simply a net- 

 work between the integument and the alimentary canal 

 forming a supporting medium for the latter. 



The Nervous System. 

 In the cyclops stage the central nervous system is the 

 same as in the adult Lepeophtheirus. The nerves supply- 

 ing the various appendages have also the same origin and 

 direction as described in that type. The nerves marked 

 4a, -tb, and 5a in Plate III., fig. 2, could not be traced. 



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