PALMEN S ORGAN IX HEPTAGENIA AND ECDYURl '-. 259 



to its natural instability. A few specimens from which the 

 organ had been thus entirely removed, lived a sufficient length 

 of time to enable studies of the behavior of the individuals, and 

 of the regeneration of some of the destroyed part - 



Becoming more thoroughly familiar with tin- structure and 

 exact position of the organ in its relation t< the vital pans ot the 

 head, a more simple method wa- de\i-ed. By mean- <>f two 

 very fine and sharp-pointed needles a small slit can be made 

 through the chitin above the organ and thru, in-crtin- a needle 

 at each side between the posterior and anterior trarlu-al tubes 

 leading to the organ, it can with some pra< -tier, be entirely 

 removed; this treatment apparently causes tin- in-ect- but little 

 pain. The four tracheal tubes were usually separated near the 

 organ though sometimes they would break off near their juncture 

 with the main longitudinal trachea?. In special for -tudics 



of regeneration of the organ, the four tubes were broken off 

 at their immediate attachment to the organ or at various drlinite 

 di-tances from it. This was possible by pressing the two point- 

 I the needles on either side of the place where the break was 

 desired. Bleeding was very rare and usually the edges of the 

 chitinous slit were brought so close together that the detection 

 ot the wound was rendered almost impossible. 



After treatment by this method the activity of the nymphs 

 \\hcn placed back into the water did not set-in to lie impaired 

 by the operation, and the wounds healed over within a leu 

 days. By this method not only was the remo\ al of the organ 

 a mvd. but mortality was reduced to a minimum. In one set 

 of experiments forty-nine out of fifty specimen- operated on 

 li\cd for more than two months after the operation. It might 

 be -aid in this connection that no regeneration of the organ 

 takes place. The ends of the broken tube- heal over within 

 t\\o or three weeks and with the e\eeption of a few small air 

 tubes which grow out from the blunt ends of the four tubes, 

 during the same time, no further growth was observed in any 

 of the specimens as long as four months after the organs had 

 been removed. Fig. 3 is drawn from a nymph in which the 

 traehe.e were broken off at their point of contact with Palmen'- 

 ,m, they almost touched but no regeneration of the organ 



