396 EMERGENCE OF DRAOONFLY-LARV.E, 



and sliglitly turwai-d into the prothorax. It never reached the 

 branchial basket and the head, nor did any get into the visceral 

 trunks via tlieir connection with the dorsals, which, in this pro- 

 nymph, lay in the anterior portion of segment 7. As no further 

 changes took place, and the pronymph was evidently utterly 

 exhausted, it was killed as described above. 



It seems to me very important to emphasise th(' vfry (/radual 

 nitd even (vppearanw of the gas in the trachese. No separate 

 hnhhles of gas were to he seen; in other words, the gas did not coiiie 

 in at separate points, but passed slowlv into the trachese over a 

 large area represented by two thoracic and four abdominal seg- 

 ments (roughly defined by the limits of the midgut). The pro- 

 cess, as I watched it, can only be compared with the slotc de- 

 velopment of a retarded photographic plate. At first, it was 

 impossible to say whether any change had taken place or not, and 

 it was only after sevei'al minutes that one could realise the steady 

 growth in distinctness of outline in the tracheie into which the 

 gas was entering. 



By great good fortune, a second e^^^ hatclied out about an 

 hour and a half after the one which I was observing. This egg 

 had been placed close alongside tlie latter, as it appeared to me to 

 be on the verge oi luitching. I had forgotten its existence, until, 

 quite suddenly, the head-capsule of the emerging pronymph ap- 

 peared in the field of \ision, and pushed gently against the pro- 

 nympli wliic-li 1 was watching. This pronymph was even weaker 

 than the one 1 had been watching, and only succeeded in getting 

 about half-way out of the egg-shell. I could not locate the 

 cephalic heart at all, and it must ha\e ceased pulsating before 

 the pronymi>h came into my field of view. As this egg-shell and 

 pronym})h were also lying on their sides, I took a fine needle, and 

 gently pushed them so that they came to lie exactly alongside 

 the one I was observing. Thus I had the midgut regions of two 

 pronymphs under observation at the same time. The most 

 important result of this was, that when the changes began in 

 the tracheal system of the first pronymph, the tracheal system of 

 the second, remaining filled with liquid, served as a most valuable 



