lo Aug.. 1910.] 



The Potato Eel-worm. 



of the worm occurs, the eggs and embryos becoming free in the decaying 

 " set " ; the eggs hatcli out and the young worms find tlieir way into the 

 soil, wliere they live till they are sexually mature ; conjunction of the sexes 

 takes place and the females bore their way into the young potatoes of the 

 new crop, there to encyst themselves again. It must be borne in mind, 

 however, that this worm can pass through its whole life cycle without be- 

 coming encysted in a tuber, as it is able to live on the decaying \-egetable 

 matter in the soil. In this case, the female does not become distended 

 with eggs, fewer being produced. 



To obtain a pure culture of 

 potato worms an affected potato 

 was carefully washed and planted 

 in sterilized soil. After a time, 

 the worms were collected from the 

 soil and the decayed " set," care 

 having been taken during the 

 period of growth to water with 

 nematode free water. By feeding 

 them on small pieces of boiled 

 potato and onion, I was able to 

 keep the worms alive and healthy ; 

 they went through their whole life 

 cycle while in the free state, and 

 slowly increased in numbers. The 

 females did not become citron 

 shaped and were quite as active 

 as the males. There were never 

 any " non-motile " larvae seen ; 

 here again mv observations are at 

 variance with the usually accejjted 

 views. 



Conclusions. 



As no experiments that we have yet tried have been successful in killing 

 the eggs and embryos, the life of the growing plant at the same time 

 beuig preserved, I can only recommend rotation of crops and pure seed as 

 a means of minimizing the ravages of this worm. No doubt, a time will 

 come when we can successfully cope with this disease, but until that happy 

 consummation of our labours is accomplished, and until we see the results 

 of the experiments at present being carried out, the above advice will keep 

 the pest in check. For not only is it good agriculture, but as the worms 

 can only change very slowly from one variety of plant food to another, 

 many of them dying in the process and many failing to beconie sexually 

 mature, and as the females produce far fewer eggs when deprived of their 

 natural food and habitat (this applies to many of the nematodes), it fol- 

 lows that by means of a suitable rotation and pure seed we will modify 

 considerably this serious problem. 



It must always be borne in mind that organic substances in the form 

 of farmvard manure are favourable to the development and spread of eel- 



FEMALE WORM AT lliK COMMENCEMENT 

 OF THE CYSTIC STAGE X 1 60. 



To give a detailed description of the many varieties of eel-worm (num- 

 ers of them new to science) found in the samples of soil and vegetation 

 submitted to me from time to time would lengthen this article^ unduly ; a 

 full account will therefore ha\e to be deferred to a future occasion. 



