ROOT-KNOT EELWORM. 229 



The eggs of the Root-knot Eelworm (see magnified figures, 

 p. 227) are stated to be oblong and bean-shaped, '08 mm. to 

 •1 mm. long ; the larva is coiled three or four times within 

 the egg membrane, and when it comes out of the egg it is 

 from "3 mm. to "4 mm. in length, and, like the adult male, it 

 is thread-like in shape, and also, like it, has at the anterior 

 extremity, in the opening of the gullet, a fine point on a 

 trilobed base, known as the " exsertile spear." 



The life-history is, that the young ivormlets tvander about for 

 a time, then presently come to rest in the plant tissues, and 

 undergo a change. The body of the larva, or wormlet, is 

 stated to enlarge, excepting at the two ends, and forms a kind 

 of " cyst," or chamber, in which the change of the Eelworm 

 to the adult state takes place. If this is to the male condition, 

 the wormlet in its chamber is stated to lengthen and become 

 more slender and thread-like, until it is curled round several 

 times within the chamber formed of its old larval skin ; and 

 when the change is complete, it breaks forth, roams in search 

 of its very differently shaped mate, pairs, and dies. Its 

 measure when full-grown is about one millimetre (the twenty- 

 fifth of an inch) in length, and only the seventeen-thousandth 

 of an inch at the middle, tapering to about half this width at 

 the extremity at the head end, in which the oesophagus, or 

 gullet, is placed, which is furnished at the foremost end with 

 a minute needle-like point (sometimes known as a mouth - 

 spear, E. A, 0.), which can be thrust out and retracted, and 

 rests on a trilobed base. It will thus be observed that these 

 male Root-knot Eelworms, from the time they quit the egg up to 

 the perfectly developed condition, preserve the same thread-like, 

 or fine eel-like, shape. 



But in the case of the female the transformations accom- 

 panying 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. 227). "About the time the 

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

 transformations, 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) continues to distend until in age its body is tilled with 

 eggs and young larvae." And, "As the embryos are developing, 



