ASEXUAL BREEDING AND PREVENTION OF 

 SENESCENCE IN PLANARIA VELATA. 



C. M. CHILD. 



In an earlier paper 1 the asexual life-cycle of Planaria was 

 described and it was shown that senescence leads to fragmentation 

 of the larger part of the body, the fragments encysting and under- 

 going, like other isolated pieces, reconstitution into small whole 

 animals which when they emerge from the cysts are physiologically 

 young and capable of growth and repetition of the life-history. 

 So far as known this is the only method of reproduction in the 

 localities about Chicago where these worms are found, sexual 

 reproduction never having been seen during some twelve years 

 of observation. 



I. ASEXUAL BREEDING. 



In order to determine whether repeated asexual reproduction 

 was possible without senescence of the stock the asexual breeding 

 of the animals was begun in the spring of 1911 with a stock of 

 animals collected from a temporary ditch in which the species 

 was abundant. In the attempt to find suitable foods the stock 

 was given varied food including lean beef, liver, kidney, earth- 

 worm, fresh water mussel, crayfish, etc. In course of time it was 

 found that the life-cycle could be considerably modified by 

 different kinds of food and the results of the feeding experiments 

 will be presented in another paper. After several months beef 

 liver was found to be the most satisfactory food among those 

 tested and has been the sole food of the stock since the early 

 months of the experiment. 



The worms of the stock collected in April, 1911, reached the 

 end of their growth period, ceased to eat and began to fragment 

 two to three weeks later and the cysts being kept in an abundant 

 supply of fresh water during the summer, the young animals 



1 "The Asexual Cycle of Planaria velata in Relation to Senescence and Rejuve- 

 nescence," BIOL. BULL., Vol. XXV., No. 3, 1913. 



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