50 Diseases of Truck Crops 



young larvae either remain in the tissue of the host 

 plant in which they have emerged, or, as is more often 

 the case, leave the host and enter the soil. This is 

 the only period during which the worms move about 

 to any great extent in the soil, where they either 

 remain for some length of time or immediately pene- 

 trate another root of the host. The nematodes in 

 most cases become completely buried in the root 

 tissue, establishing themselves in the soft cellular 

 structure which is rich in food. The head of the 

 worm is provided with a boring apparatus consisting 

 of a sharply pointed spear, located in the mouth. 

 This structure not only aids it in getting food but is 

 also valuable in helping the young worms to batter 

 through the cell walls before becoming definitely 

 located. The two sexes during the development are 

 undistinguishable up to fifteen or twenty days, both 

 being spindle-shaped. In the molting or shedding 

 of the skin, there is a marked change in the case of 

 the female, especially in the posterior region of the 

 body, which no longer possesses a tail-like appendage. 

 Fertilization occurs soon after this molt, and many 

 radical changes occur in the shape and structure of 

 the organization of the worm. The fertilized female 

 increases rapidly in breadth and becomes a pearly 

 white flask- or pear-shaped individual (fig. 8 i). 

 At this stage it is far from being wormlike and may, 

 therefore, be overlooked by one unfamiliar with the 

 life-history of the eel worm. The adult male is much 

 like that of the young female larvse, being spindle- 

 shaped in outline. The male does not cause as much 



