A. M. Taylor 267 



The results of the foregoing experiments suggest the following 

 points. That after a long period of desiccation the black currant 

 worm loses to a great extent its power of resuming a motile existence. 

 It is shewn on the other hand that it can survive such a state with 

 comparatively slight mortality if the period of desiccation is reduced 

 by a third. 



If these results may be interpreted in the following manner there 

 is reason to believe that a time limit exists past which the majority 

 cannot live and it is suggested that the survivors difier at least in 

 regard to vitality from those which succumbed to protracted drought. 



It is also suggested that the worms which shewed a limited activity 

 after a lengthy period of desiccation were dying out — they appeared 

 totally unable to employ the usual method of progression and therefore 

 they would be unable to use the means of distribution on which they 

 rely. It is probable however even at this stage that they would be 

 able, if brought into actual contact with their plant food from which 

 they could directly draw nourishment, to become active members of 

 the community. 



The natural influences to which the worms are subjected under 

 normal conditions must be considered. They are (i) the general 

 climatic conditions, and (ii) the nature of the host upon which a 

 parasitic existence is led. With reference to the former it may be 

 definitely stated that at no season of the year is there a period of 

 drought comparable to either of the two longest experimental periods. 

 Again, when the perennial nature of the host plant is considered it 

 will be seen that no occasion arises in which quiescence would be due 

 to the failure of food supply, which condition renders quiescence 

 imperative among worms whose hosts are of annual duration only. 

 If therefore the black currant is the only host upon which the worm 

 is genuinely parasitic, it is difficult to conceive a situation in which 

 a period of prolonged desiccation would enter into the life of the 

 organism. 



Quiescence in this case would merely mean that distribution was 

 temporarily suspended and would not be a question of tiding over 

 a lean time with the probable chance of not coming into contact with 

 food at the close of that time. 



The heavy mortality under comparatively short periods of desicca- 

 tion among a group of worms well known for their vitality under like 

 conditions, would seem to be an additional proof that the black currant 

 worm differs from other described parasitic species in this country. 



Journ. of Acrric Sci. vin 18 



