!^2 Phylum Plathelminthes 



chlorine-free water. We use river or well water collected directly from 



the source. 



After the worms have been distributed in the stock pans they must 

 be treated as though in quarantine for about a month. Every day they 

 must be inspected carefully and any worm showing the slightest irre- 

 gularity in outline or surface texture must be removed. We have found 

 that the worms come to the laboratory infected with parasitic diseases 

 which develop quickly under the abnormal conditions of a laboratory 

 environment. These diseases are capable of spreading and of annihilat- 

 ing a large part of the stock. If one is to have stock reliable enough for 

 experimentation, all disease must be eliminated, and with care this 

 is easily accomplished. We always boil all water to be used on the 

 worms in order to avoid the introduction of any disease-producing para- 

 site. If at all possible, the water used should be perfectly clear because 

 we have found that even slightly muddy water reacts unfavorably on the 

 worms. 



The laboratory routine in the care of the stock is as follows. The 

 worms are washed every other day. This is done by plunging the 

 hand into a lysol solution and then rinsing until no odor of lysol re- 

 mains, for very slight amounts of lysol are highly poisonous for the 

 worms. Then with the fingers the pan is wiped over its whole surface 

 to loosen the dirty slime which always gathers. The worms settle at once 

 to the bottom and all the water is poured away and replaced by fresh 

 water. If the pan does not appear clean, this is repeated. Once a week 

 the worms are washed into freshly sterilized pans and the dirty pans are 

 thoroughly cleaned and sterilized. 



Our stock worms are fed exclusively on raw liver and they continue 

 in vigor and health for an indefinite period of time. The source of the 

 liver must be considered because not all liver has correct nutritional 

 value for the worms. For example, rat liver is poor food while beef 

 liver is almost always excellent. We use liver taken from freshly-killed 

 guinea pigs which are in prime condition. This has been found the best 

 stock feed we have tried because we can control the diet of the animals 

 furnishing the liver, and this is the determining factor in the production 

 of nutritionally correct liver. If the stock is merely being maintained 

 it is sufficient to feed once a week. The feeding is done by placing 

 a small piece of liver in each stock pan. The worms feed readily and 

 the liver is left with them for 3 or 4 hours. It is then removed and the 

 stock pans are thoroughly washed. If one wishes to develop the stock 

 rapidly, the worms should be fed twice a week. 



To rear new worms for experimental purposes it is of course only 

 necessary to cut the stock worms into pieces of suitable size and to allow 

 time for regeneration. We always cut off the posterior extremities of 



