lo J. H. Pozvers 



marked in some larvae than in others, is independent of the type 

 of larva upon which the experiment is made; robust individuals 

 become elongate, slender ones still more so. 



Winter growth, hov/ever, although the easiest, is by no means 

 the only means by which this elongation of the animal may be 

 induced. A temperature of 15'' C, provided the animals are 

 inured to it before they have reached the size at which metamor- 

 phosis is possible, produces similar though less marked results, 

 growth under such circumstances easily becoming too slow. Fig- 

 ure 4, plate II, shows such a larva, one-third of whose growth 

 had taken place in a cistern. Again, among any large number of 

 summer larvae, a very few will be found which are by nature very 

 light feeders, or which have formed some special habit inconsist- 

 ent with heavy feeding. These individuals always show the re- 

 sults of their light nutrition, frequently becoming beautifully elon- 

 gated and graceful types. In nature they frequently become very 

 large, approaching in length the limits of the species ; this is be- 

 cause the slow growth prevents metamorphosis until complete 

 maturity has been reached. 



As to the nature of this elongation it should be especially noted 

 that these animals owe none of their slenderness to emaciation. 

 The very contrary is true ; they are unusually rounded in contour, 

 and indeed not infrequently are excessively fat. I was struck 

 with this curious fact the first time that I ever had occasion to 

 contrast an extremely massive with a slender larva. While net- 

 ting 10 cm. specimens for experimental purposes, a chance 

 stroke of my dip-net brought me an astonishing specimen : 

 a perfect larva, of but 18 cm. length, yet with a head 4 cm. in 

 width. Its feet and limbs, too, were well-nigh proportionately 

 massive. Yet despite these prodigious lateral dimensions the 

 specimen was the leanest larva I had ever seen, gaunt and 

 cadaverous. 



Seeking immediately for a living specimen of its own length 

 with which to compare it, I found my largest laboratory larva to 

 be 17.7 cm. in length. Although its body seemed loaded with tis- 

 sue at every point, its head measured but 2.2 cm. in breadth, and 

 limbs, tail, etc., all with the slenderness of the type. It had been 



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