74 ASCARID^ AND FILAKID^. 



iive weeks. As many as six or even seven generations occur 

 in the year. 



To similar organisms (T. devastatrix) clover-sickness is some- 

 times due. Onions and tomatoes often apparently suffer from 

 these pests. Tulip Eoot in oats is also caused by T. devastatrix. 

 The exact part that eelworms play in plant- disease does not 

 seem to have been sufficiently worked out.-^ 



AsCAEIDiE AND FiLARIDiE. 



The Ascaridce or Round-worms, and the FilaridcB or Slender- 

 Thread-worms, are found in animals and man in various positions, 

 but especially in the intestine. They are often present in very 

 large numbers, yet seldom cause any serious constitutional dis- 

 turbance. They are not only found in man, the horse, pig, dog, 

 and cat, but also in many cold-blooded animals. 



The Ascarida; are characterised by the following features : 

 Body fairly stout. Mouth triangular, and furnished with three 

 lips with papilla? (fig. 27, f). One is directed towards the 

 dorsal surface, the other two meet together in the ventral line. 

 The male has the end of the body curved, and armed with 

 two spiculse or sickle-shaped hooks (c). 



The Filaridce, on the other hand, may be identifi.ed by the 

 following : Body elongated, longer than the Ascarids. Thread- 

 shaped. Six oral papillre often present ; sometimes there is a 

 horny oral capsule. There may be two spicule which are 

 unequal or only one, a,lso four praj-anal pairs of papillas and 

 an unpaired papilla occasionally. 



The Ascarida; all live in the gut of various animals, especially 

 in the small intestine. The Filaridw take up their abode in the 

 connective tissues. 



The most typical Ascarid worm is the large round worm 

 found in the horse, called A>M:ark megcdocephala. It is the 

 largest species of the genus AfuwL^. It is yellowish-white in 



1 From observations recently made on clover sickness, I feel confident 

 that eelworms have little to do with its origin. 



