i 5 6 



NEMATHELMINTHES 



CHAP. 



ness," and forms galls or swellings on the roots of many plants, 

 in England especially on the roots of tomatoes and encumbers. 

 The free larvae live in the earth and make their way into 

 the smaller rootlets ; here the female larvae shed their skin, lose 

 their characteristic Nematode form, and become citron -shaped 

 (Fig. 78, D). The male larvae undergo a change, and after 

 a period of rest cast their skin and, leaving the rootlet, seek 

 out the females. The female does not undergo this second 

 ecdysis, but its generative organs grow and mature in what is 



Fig. 78. A, Male Ile- 

 terodera schachtii 

 strongly magnified ; 

 a, head lappets ; b, 

 mouth cavity ; c, 

 spine ; d, muscle 

 of spine ; e, gland ; 

 /, oesophagus ; g, 

 bulb ; h, nerve -ring ; 

 i, excretory pore ; j, 

 intestine ; A;, testis ; I, 

 intestine ; m, muscles 

 moving spicule ; n, 

 spicule : B, first mo- 

 tile larva : C, second 

 immovable parasitic 

 larva casting its skin : 

 D, a female with one 

 half of the body- 

 wall taken away tc 

 show the coiling 

 generative organs ; 



a, boring apparatus ; 



b, oesophageal bulb ; 



c, excretory pore ; d, 

 alimentary canal ; e, 

 anus ; /, ovary : E, 

 a male shortly be- 

 fore casting its larval 

 skin. 



practically a larval stage. The embryos develop within the body 

 of the mother, and, escaping through the uterus, ultimately cause 

 her death. They then make their way into the earth. The cycle 

 of the development takes but four or five weeks, so that, as in the 

 case of Tylenchus devastatrix, there are several broods in a year ; 

 T. tritici, on the other hand, has but one. 



Vuillemin and Legrain 1 point out that while Heterodera is 

 injurious to cultivated plants growing in damp soil, its pres- 

 ence is advantageous to those that grow in deserts. It is very 

 common in the Sahara, and attacks many plants which are 



1 C. R Ac. Sci. cxviii. 1894, p. 549. 



