17 



It cousi.sts (tf three portions, two moderately large 

 masses on the lateral margins of the cephalo-thorax, 

 just behind the antennules, and a median, smaller one, in 

 front of the base of the month. The lateral portions are 

 connected with the median bv a dnct. The median por- 

 tion g-ives oif a duct, which passes posteriorly along- the 

 (esophagus and enters the caecum, at the anterior end of 

 the stomach. When the parasite is first removed from the 

 fish the digestive gland is usualh* of a dark brown colour, 

 but after starving for a few weeks it becomes colourless. 

 The product of the gland is a pale, yellow iiuid, which 

 can be seen as it passes along the duct between the lateral 

 and median portions. 



Situated between the first and second pairs of thoracic 

 feet is a pair of glands visible in the living animal as 

 blown spots. A minute duct passes downward and then 

 forward along the stomach. The duct appears to enter 

 the stomach near the posterior end. 



The food of this parasite is said to be mucus, and blood 

 has not been detected in the stomach."^' This fact gives 

 ."onie cause for the opinion advanced by many Zoologists 

 that Lepeophtheirus and other allied genera are therefore 

 not parasites in the strict sense of the term, and may not 

 be hurtful to their hosts. There is considerable dithculty 

 in settling the question of their true food. tSpecimens 

 taken direct from the living fish and placed under the 

 microscope, rarely show even the faintest trace of red 

 colouring matter in the alimentary canal. The difference in 

 structure between the Ualigidae and the obviously blood- 

 sucking Lernese is very great. This will be pointed out 

 in the section dealing with Lerncea hranchialis, and may 

 account for the apparent absence of blood. Mucus at the 

 best is a poor food, but Lepeophtheirus can live for upwards 



* They do not hesitate, however, to eat their comrades when these 

 become feeble. 



