SOME AQUATIC WORMS, ETC. 181 



usually extending from the pharynx to the posterior 

 border. In some it is simply a great sack, receiving all 

 that the mouth and pharynx turn into it ; in others it 

 divides into many branches whose terminations may be 

 seen near both sides of the body. The stomach seldom 

 has a posterior opening, for, as a rule, there is no intes- 

 tine. After the nutriment has been digested from the 

 food, the insoluble remains must be ejected through the 

 mouth. It is no unusual sight to see one of these ciliat- 

 ed worms vomit up a mass of indigestible and empty 

 Ehizopod shells, Eotifer carapaces, with many unrecog- 

 nizable particles and fragments. They seem to prefer 

 animal food, usually selecting Rhizopods and Rotifers, 

 but they are as fond of Infusoria, which must be as 

 nourishing and more easily digested. I have more than 

 once lost an interesting specimen of Infusorium because 

 one of these Turbellarian worms had been included un- 

 der the cover-glass : there were a worm and an Infuso- 

 rium ; a pause, a single snap, and only the worm re- 

 mains. 



They are propagated in two ways by eggs and by 

 transverse fission ; that is, one worm divides across the 

 middle and so makes two, each of these again dividing. 

 And often before the division has been accomplished 

 both halves are also partly divided, so that the single 

 body seems to be formed of several incomplete worms. 

 The eggs of the commonest species are brownish egg- 

 shaped bodies, dropped anywhere in the mud or water, 

 or they may have a stem which attaches them to sub- 



