ELISHA MITCHELL SCIENTIFIC SOCIETY. 93 



entrance to the healthy tissues of the root. The plant, not able 

 to expel the invader, bends its energies in a vain endeaver to 

 repair the injury to the roots. Increased development of cells 

 takes place, and normal ones are turned from their proper posi- 

 tion and function and also very much enlarged. The result is 

 the formatiiin of a gall, an increase of tissue in the root, which 

 supplies food and protection for hundreds of the worms, all 

 which lessens the energies of the plant nor.ually directed to the 

 production of leaf and fruit. 



The larvae wander for a time through the tissues and finally 

 come to rest. Plate VI, Fig. 39, represents a larva as it is 

 wandering through the tissues of a potato tuber. It now moults 

 the second time and passes into a truly parasitic condition. 



Cystic State. — The larvae locate at various depths in the 

 tissues. The body now begins to enlarge, except at the two ends. 

 Speaking vulgarly, it would be said to "swell up." Alaiost 

 before any increase in size of this part of the body is noticed 

 the worm becomes rio-id and could not move if it would. Its 

 body may be turned or twisted in very curious shapes when this 

 rigidity or fixedness comes upon it. (See Plate IV, Fig. 17a.*). 

 The enlargement begins close behind the muscular bulb oi' the 

 oesophagus, and for a little time this part of the body is larger 

 than the posterior part. Very soon the enlarging takes place 

 all along the body to the hyaline space near the tail end, and 

 this portion of the cyst becomes generally of a greater diameter 

 than the anterior part. The cyst is at first rudely spindle- 

 shaped, then c'avate (or club-shaped), with a very small sharply 

 pointed process, the tail, at the larger end. Fig. 18 represents 

 the spindle form, 19 the clavate form. Up to this point it is 

 difficult to distinguish the sexes, but from this point they sharply 

 diverge. The iemale cyst continues to enlarge, while the male 

 undertroes a wonderful transformation and returns to the thread- 

 like or anguillula form. 



Transformation of the Male. — The bodv of the male at 

 this point is the same size as the interior of the cyst, very stout 

 in proportion to its length. The first sign of a transformation 

 7 



