WORMS, 231 



The Root-knot Eelworm {Heterodera radicioola). 



This second species of the genus Heterodera de- 

 velops much like the beet eelworm, living like it on 

 the roots of plants, but more deeply within them, so 

 that the body of the female (which swells till it 

 becomes pear- or flask-shaped) does not cause the 

 outer part of the infested root to project, and does 

 not reach the exterior. Where the eelworms collect, 

 galls are formed which decay later on, when the 

 eel-shaped larv^ escape into the soil, very soon, how- 

 ever, to enter the roots again at their slender tips. 

 The galls are thickenings in the course of the root, 

 and are never lateral appendages, like, for instance, 

 the well-known " tubercles " in the roots of legu- 

 minous plants (e.g. clover, pea). The root eelworm 

 lives in the roots of more than fifty plant species in 

 the most various parts of the world, and infests both 

 weeds and cultivated plants. It is especially damaging 

 to clover and lucerne, in which not only the galls die, 

 but also all parts of the root below them. In this 

 country the roots of cucumber and tomato are some- 

 times attacked (E. A. Ormerod). 



CLASS: PLATYHELMIA (FLAT WORMS). 



Flat worms have a flat, generally leaf-like body, 

 and usually no body-cavity, the space between the 

 internal organs and the muscular body wall being 

 filled up with connective tissue. 



I will only deal here with the orders of Tapeworms 

 (Cestoda) and Flukes (Trematoda). 



Oedee: Cestoda (Tapeworms). 



The external characters of an ordinary tapeworm 

 may be gathered from Figs. 135 and 136. A very 

 small " head " continued behind into a small " neck " 



