186 FREDERIC H. KRECKER. 



The size of a given wave is maintained by carrying along the 

 fluid in its path. As a result of the trailing fluid there is always 

 some of it all along the coelom. This residuum explains the 

 arrival of small quantities of fluid at a given end with the peri- 

 stalsis which precedes the arrival of the primary wave. The 

 free play between uterus and body wall explains also why all of 

 the fluid is not carried away from an end with the first peristaltic 

 wave but is instead taken off in lessening quantities by several 

 waves. 



What relation the movement of the ccelomic fluid has to the 

 well-being of the adult worm or its young depends upon the 

 general function and composition of the fluid. Very little definite 

 information has been published regarding this matter for the 

 nematodes in general, and nothing, so far as I am aware, on the 

 fluid of the genus Camallamis. It has been suggested that one 

 of the functions served, in some cases at least, is to act as a 

 medium for oxygen. If this be true the circulation in the present 

 instance can be looked upon as of value in effecting a thorough 

 distribution of the available oxygen. 



There is some reason for believing that the circulation is of 

 particular benefit to the young. Pointing to this conclusion is 

 the fact that the peristaltic waves very effectively stir up the 

 young and constantly bring different individuals into contact 

 with the walls of the uterus and therefore nearer the ccelomic fluid. 



From present knowledge it is rather hard to conceive what 

 other purposes than those suggested would be served by such 

 rhythmic constrictions of the uterus. Especially is it hard to 

 see why there is a continual stirring up of the embryos bringing 

 successively different individuals into contact with the walls of 

 the uterus as is done in this case if it were not for some purpose 

 connected with the surrounding medium. There is, however, a 

 rather extensively held opinion that the cuticle of nematodes is 

 impervious to all but the strongest fluids and even in some cases 

 to strong formalin. If this were true the cuticle could possibly 

 prevent absorption of oxygen. The view just mentioned is 

 based on such examples as the vinegar eel, and on some instances 

 in which adults of other species or their contained embryos have 

 resisted preserving or fixing reagents for a considerable length 



