796 PROFESSOR J. STEPHENSON ON 



the level of the sand, in which the specimens partially embed themselves when they 

 are free to do so. 



The appearances above described may be seen to occur both when the animals are 

 at rest and when they are moving. They may be absent after a long period of 

 quiescence, — for example, in the morning, when the specimens have probably been 

 motionless for some time ; in this case the animals seem to need wakening up before 

 the phenomena can be manifested ; after the animals have been handled and made to 

 crawl about, the expulsion of water begins in the way described. 



The interval between successive jets of a series is very fairly regular in the same 

 animal, but it varies in different animals, or at different times in the same animal ; in 

 four observations it was 22, 13, 13, and 18 seconds. 



The question remains to be answered, Where is this water taken in ? It seems most 

 natural, having in view the phenomena of intestinal respiration in other Annelids, to 

 suppose that it enters at the anus in the intervals between the jets. This however is 

 not the case. During the intervals the anus is closed ; and even granting that a 

 minute quantity of water might possibly be introduced between the lips of the anus by 

 means of ciliary action, this would be very far from furnishing, in the few secouds 

 available, the considerable amount ejected. 



The next possibility is that the water is both sucked in and ejected during the time 

 the anus is open, — first rapidly sucked in, then immediately expelled. The jet on the 

 surface, however, makes its appearance directly the anus opens ; in the experiment 

 where a wall of sand was built up behind the animal, the sand was blown away quite 

 at the beginning of the open period ; and observation, even under a lens, with carmine 

 particles in the water, fails to detect any inhalant currents at the anus at any period 

 of the cycle. 



It would seem, therefore, that since the water is not introduced at the anus, it must 

 enter by the mouth. The following experiment was next performed : — A specimen was 

 left for half an hour in water containing carmine in suspension ; it was then taken out 

 and washed, and put into a white dish with clean water ; it was now observed that the 

 water ejected from the anus was carmine-tinted. After about six jets, when things 

 began to be a little obscured, the contents of the dish were replaced by clean water ; it 

 was then easy to see that the fluid expelled from the anus was still coloured. The 

 water in the dish was again renewed after another five jets, again after five more, and 

 again after about six more jets, the ejected water being tinted throughout. Finally, 

 after about six further jets had been expelled, the animal was once more placed in clean 

 water, and observation against the white background showed that the ejected fluid was 

 still slightly coloured. A considerable amount of water containing carmine must 

 therefore have been present in the alimentary canal when the specimen was first placed 

 in the clean water ; and the double series of intestinal caeca in this species at once 

 suggest themselves as its probable receptacle. 



If, now, an animal, while regularly expelling water from its anus, be placed in a 



