NEMATODA MERMITHIDAE 



i53 



embedded in a fatty parenchyma which nils all the space within 

 the skin. 



Atractonema gibbosum, which lives in the body-cavity of the 

 larva of Cecidomyia pini, has a similar life-history, bnt the parasitic 

 form has a structural peculiarity which merits attention (Fig. 75). 

 At the time of sexual maturity a swelling, which is caused by the 

 prolapsus of the uterus and vagina, appears at the posterior end 

 of the body ; this swelling increases until it equals the rest of the 



Fi G . 76. Four stages in the life-history of Sphaerularia bombi Dufour, ?. (From 

 Leuckart.) A, Beginning of the protrusion of the uterus (b), x 66 ; B, later stage, 

 x 66 ; C, later stage, x 12 ; D, the protrusion is complete, x 6. In each case a 

 represents the Nematode, and b its protruded uterus. 



body of the Nematode in size. Even this is far surpassed by a 

 similar protuberance in Sphaerularia bombi, where the evaginated 

 sac grows with such extreme rapidity that in a few weeks its 

 length increases from - 25 mm. to 15 mm. and its volume 60,000- 

 fold, the increase being due, according to Leuckart, to the increase 

 in size of the individual cells and not to their multiplication. 

 The Nematode which has produced this enormous growth gets 

 relatively smaller and smaller, and ultimately drops oft' (Fig. 76). 

 The sexual larvae which arise from the eggs in this sac leave the 

 body of the bee in which this species is parasitic by the anus, 



