PLATE 4 



EXPLANATION OF FIGURES 



16 Photogenic organ of full-grown larva of Photuris pennsylvanica, ventral 

 view. N, nerve; P, luminous layer; U, urate layer. 



17 Section through a fat sphere of pupating larva of Photinus consanguineus. 

 FB, fat haemocyte; /, cap or investment; K, nucleus of fat cell; R, rupture; SB, 

 segmental haemocyte. 



18 Section through fat sphere at a later stage than preceding; the invest- 

 ment /, is thicker and more constricted and the fat haemocytes FB, far more 

 numerous. 



19 Section through remnants of fat spheres and investments; lettering as 

 in figure 17. 



20 Fat and blood cells in Photinus consanguineus, one day out of the egg. 

 A, fat cell; B, blood cell. 



21 Fat cells in Photinus consanguineus, sixteen days out of the egg. 



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