103 



cated by the presence of at least one other species of parasitic Nema- 

 tode. It has al'eady been stated that the ova of Heterodera are as a 

 rule enclosed in the body of the female parent, the cyst or egg-sac. 



The microscopic examination of the specimens first taken of the 

 roots showed, in both the knobbed and the dotted rootlets, the presence 

 of nematode ova differing in shape and especially in size from those of 

 H. radicicola. They were also irregularly scattered through the tissues 

 of the root, being accumulated in small numbers in some places, in 

 large numbers in others, and sometimes were found in single specimens. 

 It appears that these ova cannot be derived from the pear-shaped and 

 motionless worms, but must belong to a species the adult females of 

 which are wandering freely within the root, depositing their eggs 

 gradually as they wander about. No trace, however, was found of the 

 females themselves ; whereas the larvae already hatched from their 

 eggs, and clearly differing in size and shape from those of the first 

 species (H. radiciola), were found both within the roots and outside in 

 the earth adhering to their surfaces. 



In the latter case they were sometimes considerable in number, and 

 they showed signs of advanced growth. They were of various sizes, 

 the most advanced showing the first signs of genital organs, preserv- 

 ing, however, at the same time, their original shape, viz. : a blunt, 

 almost rounded tail, and a fine short dart within the mouth-cavity. 

 From the fact also that no full grown individuals were discovered i > 

 the soil, it appears that they do not exist at the present season (De- 

 cember to January). 



Owing to the absence of full-grown animals, it is impossible to de- 

 termine the species, though probably it is one hitherto unknown. There 

 can, however, be no doubt that the young worms found in the soil will 

 finally return to the roots to accomplish their development, thus 

 gradually infecting the whole soil, as previously explained. Owing to 

 the numbers in which they exist, it appears that this unknown species 

 plays a far more important role in bringing about the disease in tho 

 present case than the species first described. It is also likely that to 

 their presence may be attributed the dying off of the small lateral off- 

 shoots of the roots mentioned previously, though the evidence at pre- 

 sent available dot s not permit of a definite opinion. 



It is not improbable that even a third species of nematode is in- 

 volved in the present Banana disease, for in some instances there were 

 found in the adhering earth, and amongst the larvae of the two forms 

 previously described, young worms, which could not possibly belong t > 

 either owing to their shape, but which possessed the fine, sharp pro- 

 trusive dart in the mouth-cavity. The number present, however, was 

 very limited. Such is the result of microscopic examination, from 

 which it seemed to be sufficiently clear that the nematodes are tho 

 cause of the disease, and that the second and unknown species des- 

 cribed is by far the most injurious. 



The most important question to be considered is how to cope with 

 the disease; in other words, how to prevent the propagation of thj 

 worms. This can only be arrived at through an exact knowledge oi 

 the life-history of the pests. 



In order to arrive at this, an examination at one season of the ye r 

 will not suffice, and with the advent of warmer weather further obser- 



