IS4 FREDERIC H. KRECKER. 



which becomes filled with ccelomic fluid. This constriction 

 moves as a wave lengthwise of the uterus and carries fluid along 

 because the latter cannot easily escape. 



The description of the entire process is as follows, beginning, 

 for the sake of convenience, when the fluid leaves the posterior 

 end. The peri-uterine space of this end is at this time filled 

 with ccelomic fluid for approximately one-sixth of the worm's 

 entire length. A peristaltic wave arises at the posterior end 

 of the uterus and moves anteriorly. This is followed by another, 

 then a third and sometimes a fourth. Each wave carries with 

 it some of the fluid, the first taking the largest or primary wave 

 of fluid, the third or the fourth, if there is a fourth, taking the 

 least. The three waves all leave within seven seconds- at slightly 

 over two second intervals. After the last wave has left, only a 

 thin film of fluid remains in the peri-uterine space. At about 

 the time when the first of the peristaltic waves starts from the 

 posterior end of the uterus, posterior to anterior waves of peri 

 stalsis are to be seen at its anterior end, each of them pushing 

 along a little fluid. It was rather difficult to watch both ends 

 of .the worm at the same time and so my observations on what 

 were practically synchronous occurrences may be subject to 

 slight error. There are usually three of these peristaltic waves 

 at the anterior end and then, with the fourth, comes the primary 

 wave of fluid from the posterior. This wave arrives at approxi- 

 mately the time when the third wave is leaving the posterior end. 

 The circulation is therefore a rather sluggish process since the 

 time between the first and the third waves is seven seconds and 

 the entire length of the worm is only twenty-five millimeters. 



As soon as approximately one sixth of the ccelom at the 

 anterior end has been filled with fluid, anterior to posterior 

 peristalsis begins at this end and continues in the manner just 

 described for the posterior end ; a primary wave of fluid leaves, 

 followed by a second and a third and sometimes a fourth, the 

 first wave being the largest and each succeeding one smaller. 

 There is this difference, however, between the processes at the 

 two ends; when a peristaltic wave arises at the anterior end of 

 the uterus it pushes ccelomic fluid both anteriorly and posteriorly 

 instead of sending it all posteriorly. This movement in opposite 



