]30 TOMATO. 



The eggs of the Root-knot Eelworm (the H. radiclcola) when 

 mature are about three to four thousandth of an inch m length, and 

 from then' transparency the changes in appearance accompanying the 

 growth of the contained wormlet may be observed within. Two forms 

 of these are given in figures at p. 127, copied (and here acknowledged 

 with thanks to the skilled observer) from Prof. Geo. F. Atkinson's 

 plates. 



The young root-knot wormlet (the larva, technically) is stated, 

 when it comes out of the egg, to be from twelve to sixteen thousandth 

 part of an inch in length, and (like the adult male) thread-like in 

 shape, and like it has an " exsertile spear " with a trilobed base. These 

 larvas, having wandered about for a time, come to rest in the plant 

 tissues, and undergo a change. The body of the wormlet is stated to 

 enlarge, excepting at the two ends, and become rigid, so as to form a 

 kind of chamber, or "cyst," in which the final change of the wormlet 

 takes place to the perfect condition of male or female as the case may be. 

 In fact this condition may be compared (in the case of the male) to the 

 chrysalis state of some insects in which the maggot skin hardens, and 

 the moth or fly forms within. 



But in the case of the Root-knot Eelworm a very remarkable form 

 of transformation takes place. In due time the male (after continuing 

 to lengthen, and become more slender and thread-like until it is 

 curled round several times within the " cyst " formed of its larval skin) 

 completes its moult, and breaks forth from the cyst, and roams in the 

 tissues until it finds its mate, when it pairs and dies. But in the case 

 of the female the transformations accompanying development are very 

 different. The male, as noticed, moults and comes forth from the 

 " cyst," or old skin in which it has advanced to maturity; but (still 

 abridging from Prof. Atkinson's observations) it is noted : — " The 

 female does not moult again, but continues to enlarge enormously 

 until it is gourd-shaped" (see figures at p. 127). " About the time 

 the ' cysts ' have reached the stage when the male begins its transfor- 

 mations, it is easy to distinguish the female cyst. This continues to 

 enlarge or ' swell ' until the tail part is cast and thrust aside, and the 

 body is sometimes so much swelled at the posterior end as to cause a 

 noticeable depression at the opening of the vulva. 



"Fertilization is stated to take place long before this gourd- or 

 pear-shaped cyst has ceased enlarging, this (that is, the female) con- 

 tinues to distend until in age its body is filled with eggs and young 

 larvse." And, " As the embryos are developing, the body of the cyst 

 breaks up into an amorphic gelatinous mass, in which the young 

 larvae and eggs are found floating within the cyst cavity. Length of 

 life cycle, one month." — (G. F. A.) 



From the above notes it will be seen that amongst the main 



