'2'J2 A. S. PEARSE. 



drawn into the cloacal chamber by closing the opening to the 

 respiratory trees 2 and contracting the radical muscles r, which 

 extend from the cloaca to the body wall. The cloacal opening 

 / is then closed, the respiratory tree aperture 2 is opened, and 

 the contraction of the walls of the cloaca forces the water into 

 the respiratory trees. Sometimes the cloacal opening / is kept 

 closed while the water is forced back and forth from the cloaca 

 to the respiratory trees, but the water is usually expelled from 

 the body after each inspiration. When an individual is placed 

 in shallow water so that the terminal opening / is just below the 

 surface, the water is often expelled with enough force to form a 

 fountain-like "spout" 3 or 4 cm. high. 



The rate of the spouting reactions varies considerably, as is 

 shown by the following observations, made upon two individuals 

 which were buried in the sand. The average time between 144 

 consecutive spouting movements was 39 seconds for one animal ; 

 and the average time between 24 spouts was thirteen seconds for 

 the other. In order to ascertain what would happen if these two 

 individuals were prevented from spouting for a long period of time, 

 they were first observed as they lay buried in the sand and the 

 rate of their normal respiration noted. They were then made to 

 pull the posterior end down into the sand by poking it with a glass 

 rod, and whenever it started to emerge it was poked so that it 

 was again withdrawn. The first animal spouted every twenty 

 seconds (seven times) before being prevented from breathing and 

 was then kept under the sand for one hour and twenty minutes. 

 After the posterior end had appeared again there were no spout- 

 ing movements for four minutes, and the next seven spouts 

 averaged 36 seconds apart. The other animal averaged thirteen 

 seconds between 24 spouts before its breathing was prevented. 

 It was kept under the sand for two hours, 36 minutes and forty 

 seconds ; and at the end of that time it spouted with the posterior 

 end still buried in the sand. The next nineteen spouts averaged 

 one minute and five seconds apart. In both these instances the 

 rate of respiration was more rapid before the breathing movements 

 were prevented than afterwards. That is, an individual breathed 

 more slowly after it had been made to " hold its breath " for an 

 hour or two than it had before. This result can be accounted 



