WORMS. 227 



become sexually mature, and lay eggs (600 to 1600), 

 from which are developed the larvae that inhabit later 

 on the cockle-seed like gaUs. The disease is known 

 in England, Germany, France, and Italy, and is 

 especially harmful in Saxony, where it sometimes 

 attacks a quarter of the wheat crop. Remedies: 

 Either there should be no ear-cockles in the seed corn, 

 or else the eelworms should be destroyed in them. The 

 infested grain may either be put through a sieve, or else 

 soaked for twenty-four hours in weak sulphuric acid 

 (one pint strong acid to thirty-three gallons of water), 

 when many of the galls float and can be skimmed off, 

 while the eelworms are killed in those which sink. 



The Beet Eelworm (Heterodera SchachtU) ^ 



is the cause of the " beet sickness " of the soil. The 

 course of the disease is as follows. At the end of 

 July light-coloured patches are found here and there 

 among the normally developed beet. The leaves are 

 weak and limp, and the outer ones especially get 

 yellow, spotted, and die off. Later on the inner 

 leaves die as well, after which the top of the beet 

 becomes black and the whole root gradually decays. 

 In less severe cases the beet may recover towards 

 autiimn and develop new heart leaves, but the roots 

 remain small and the crop is poor, often being only 

 one-third of its normal amount. Kiihn has proved 

 by infection experiments that the sole cause of beet 



^ Fig. 134. — The Beet Eelworm (^eferodera ^cAocAWt) : 1, A beet root with adult 

 females attached (natural size) ; 2, a lateral rootlet of beet which Eelworm larvffi (a) 

 are penetrating (enlarged) ; 3, a lateral rootlet of beet with swelling (a) of the outer 

 akin caused by the excessive development of larvae which have previously entered it, 

 and which have now become nearly mature females (enlarged) ; 4. a just-hatched 

 larva ; 6. a larva which has penetrated a root and swollen up into a club-shaped form ; 

 6-8, development of the male; 9, a nearly adult and, 10. an adult female. The 

 following letters have reference to Figs. 4-10 : a, mouth spine, — b, sucking stomach 

 (pharynx), — c, d, intestine, — e/, rectum,—/, anus, — g^ excretory organ ; h (in Figs. 

 4-7). rudiments of the sexual organs in the undeveloped larvae ; h (in Fig. 8), testis ; 

 i (in Figs. 7 and 8), copulatory spicules of the male ; A; (Figs. 9 and 10), ovary ; 

 I (Figs. 9 and 10), female sexual opening; m, nerve ring; wi (Figs. 6-8), larval 

 skm; W2 (^^igs- 6-^)) ^^^ si^i° which the developing male forms within the larval 

 skin. Figs. 4 and 6 are magnified more than Figs. 6-10. 



