204 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



It consists of 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 mouth. The lateral portions are 

 connected with the median by a duct. The median por- 

 tion gives off a duct, which passes posteriorly along the 

 oesophagus and enters the caBCum at the anterior end of 

 the stomach. When the parasite is first removed from the 

 fish the digestive gland is usually of a dark brown colour, 

 but after starving for a few weeks it becomes colourless. 

 The product of the gland is a pale, yellow fluid, 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 

 brown 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 

 some 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 difficulty 

 in settling the question of their true food. Specimens 

 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 Caligidse and the obviously blood- 

 sucking Lernese is very great. This will be pointed out 

 in the section dealing with Lerncea branchialis, and may 

 account for the apparent absence of blood. Mucus at the 

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



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

 become feeble. 



