20 



occupy a longer time. Oviposition is also arrested if the Arguli 

 are deprived of food. The number of eggs laid vary from 300 to 

 500, and I have a record of one Argulus of 633 eggs laid at inter- 

 vals. Eggs are laid in rows of from three to six broad. 



Whilst ovipositing the three first pairs of feet are in motion, the 

 fourth pair being held rigid, with their bases (which are somewhat 

 prominent) pressed together over the entrance to the oviduct, as in 

 the act of straining. After depositing an egg the Argulus raises 

 itself higher up on the object on which the eggs are laid, and, moving 

 a little from side to side, causes the eggs to be placed in proper order 

 in the several rows. The average time occupied during the de- 

 positing of each egg is eight seconds. I have already described 

 under the heading of female organs the mode of self-fecundation 

 of the egg by means of the papillae, and I have only to add that the 

 protuberances at the base of the fourth pair of feet materially assist 

 the Argulus during this operation. The Argulus generally dies soon 

 after completing ovipositing. I have noticed that ova laid in con- 

 finement are invariably fertile. My experiments were carried on by 

 means of test-tubes blocked with cotton wool and placed in the 

 shade at a moderate temperature. 



Concluding Remarks on the Habits and Life History. 



To the casual observer the most noticeable feature of the Argulus 

 is the incessant motion of the swimming-feet, in which the four pairs 

 participate simultaneously. The pair of foot-jaws have an indepen- 

 dent movement. The Argulus frequently makes a series of somer- 

 saults, and when about to attach itself to its host the current of 

 water caused by the movement of the fish's fins gently carries it on 

 to the fish. When once attached by means of the powerful suckers, 

 all efTforts of the fish to shake it off are in vain. The movement of 

 the swimming-feet just described is never arrested during life, even 

 when the Argulus is at rest on its host, or when ovipositing. 

 Occasionally one sees the Argulus maintain for an hour or more a 

 whirling motion. 



The food of the Argulus is blood-plasma, procured by means of 

 the proboscis and mouth organs. The incision made on the fish is 

 very minute, but a good deal of inflammation is evident. The 

 favourite position of the parasite appears to be the gills, but it is 

 also found on the fins and tail, underneath the gills, and even on 

 the eyes. They remain attached without once leaving their host for 

 as much as three or four days at a stretch; in fact, the newly-hatched 

 Arguli immediately attach themselves to the fish, and only leave it 

 to undergo their metamorphosis. On the other hand, the newly- 

 hatched larvae have been known to live five days without the host, 

 and I have a record of an adult Argulus living fourteen days without 

 food. Soon after the death of the host the parasites forsake it. If 



