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vations may be made. It lias been seen that all the different species 

 pass a certain period of their life-history outside the plants them- 

 selves, that is to say, in the soil, this being a common feature in the 

 history of all parasitic animals, since it is the only means by which 

 they can spread. The time, therefore, in which to institute an attack 

 is when the majority are found in the soil; any attempt to reach the 

 pest when within the plant must be doomed to failure, for it is then in 

 perfect security. In countries where there are well defined seasons 

 with great differences between them, it is more easy to ascertain ex- 

 actly the different stages than is the case with such a climate as that 

 at Alexandria, where probably devolopment goes on steadily ; that is 

 10 say, the free worms are always present in the soil. It is, on the 

 other hand, also very likely that their numbers become considerably in- 

 creased at certain periods in connection with the subsequent genera- 

 tions. Any remedy to be applied would therefore have its maximum 

 effect only if applied during these periods. This matter can, however, 

 only be definitely decided when the life-histories of the species have 

 been followed throughout. Experiments could then be conducted 

 as to the most suitable means to employ. In coping with nematodes 

 attacking the beet crop in Germany, a method was successfully ad©pted 

 which may be memtioned here. Nematodes are found in, one might 

 say, almost every plant in small numbers. Practically all nematodes 

 living as parasites on plants are not exclusively parasitic on one indi- 

 vidual species, for if they find the necessary favourable conditions for 

 existence they will attack another host. Just as a human being or an 

 animal can carry a tape worm or other parasite without apparent in- 

 jury to health, and only show signs of suffering when the number in- 

 creases, so within certain limits can plants withstand nematodes, and 

 only show signs of disease when their numbers become excessive. 



To combat the pest in the sugar-beet plantations, other plants which 

 were suitable as hosts were used to attract the pest. The seed was 

 sown early in spring, some weeks before the beets were planted. The 

 larvae of the nematode hibernated freely in the soil and attacked the 

 newly sown plants, which were subsequently removed and destroyed. 

 There were thus removed from the soil vast numbers of the pest which 

 would otherwise have attacked the beet. This did not result naturally 

 in a complete clearance of the pest, but the beet was enabled to resist 

 the number which remained. The adoption of this method in the 

 case of Bananas would require certain modifications, but something 

 might be done in this direction ; and then, bv providing the plants 

 with suitable conditions for recovery, such as good cultivation and an 

 application of suitable manure, they may recover. 



f lhe idea has been expressed that the disease is one of recent intro- 

 duction, but this does not seem probable. Species of the genus 

 Heterodera were found by Dr. Looss in a garden at Alexandria some 

 years since, and these are similar to the Heterodera of the Bananas. 

 It is probable that they have now found a most suitable host in Bana- 

 nas, and have consequently rapidly increased in numbers They have 

 probably been living in Banana plantations for some considerable time, 

 and the result of years of increase has only now become very apparent. 



Experiments in the direction indicated should be attempted, first, to 

 ascertain plants most suitable, the time at which they should be sown, 



