INVESTIGATIONS ON THE NARCISSUS DISEASE. 59 
for a period of two months, but if allowed to remain dry for a year 
only about one-third recovered on being moistened ; the other two- 
thirds were dead. Eggs, however, of which the contents were divided 
into 2, 4, 8, or 16 divisions, could not bear desiccation for even six 
days. Eggs further advanced and containing the eelworm in em- 
bryonic condition could remain in a state of suspended animation 
for six months (possibly longer) without losing the power of recovery 
on the application of moisture. The power of larvae to regain con- 
ditions of active life after desiccation was found to be very great, 
and the results *of experiments carried out by Ritzema Bos showed 
that after suspended animation during a period of two and a half years 
they returned to their normal state. The adult Tylenchus (that is* 
those in which differences in sex are discernible) could not support 
life under desiccation. 
From the results gained it is possible to suggest some general 
principles which should guide the attempt to find effective and eco- 
nomical remedies and preventive measures. There seem to be four 
possible interrelated ways of this : 1. Rotation ; 2. Treatment of in- 
fected ground ; 3. Treatment of bulbs ; 4. Trap or " cure " cropping. 
Rotation is included among the measures of prevention as it is of 
importance to give such a rotation as will not give a crop liable to be 
attacked in immediate succession to one which is known to have been 
infected with eelworm. Oats, onions, and clover are the crops which 
suffer most severely with us ; but many other plants are liable to be 
attacked. When a field of oats or clover, for instance, is infected, it is 
difficult to clear and also to prevent the attack being carried about in 
manure, as a portion of the eelworms, very possibly most of them, 
customarily leave the dying plants and go into the soil ; some are 
carried away with the cut crop, and, being mixed up in the straw with 
farmyard manure, are presently carried out again and spread quite 
uninjured on clean fields or perhaps in the very fields from which they 
came, in readiness to attack a susceptible crop — Narcissus, for example 
— if it is planted down in such fields. 
It should also be borne in mind that eelworms can be conveyed in 
infested earth, such as clings to wheels of carts and ploughs, to boots 
of workers and to farm implements, and, from their power of pro- 
pagation, a small beginning makes much trouble. To carry out the 
rotation so as to starve out the eelworm, the crops planted must be 
immune towards nematode attack, so that the larvae in the soil 
cannot find nourishment. The crop grown should be economically 
profitable ; and, if possible, it should be such as to enrich the land, 
or at least not impoverish it. The crop should be one of vigorous 
growth, so , as to choke out all weeds or other plants which might 
harbour eelworms and permit of their development. 
An ideal method of starving out the eelworm would be to allow 
the ground to lie fallow for a long period, keeping it free from weeds 
by thorough cultivation. It is evident that by such a method the 
