N o . 4 . ] MET, I MORPHOS1S OF THE FLAG J \'EE VI L . 187 



Fig. 6 shows the leg of a young pupa within its sheath. All 

 the leg segments are rapidly assuming their definitive form. 

 The fourth tarsal segment has reached its maximum develop- 

 ment ; it will be relatively smaller in the adult. The broad, flat, 

 brush-bearing pads of the third tarsal segment are here big bag- 

 like dilatations. Corbel and scrobe are very evident upon the 

 tibia, and the femur and 

 other segments are full of 

 fat, rapidly being metamor- 

 phosed into muscle. 



Fig. 7, A, represents the 

 structure of the tarsus in 

 an old pupa ; externally it 

 is practically that of the 

 adult beetle. Fig. 7, B, is 

 another section in the same 

 series, passing through one 

 of the lateral pads of the 

 third tarsal segment. It 

 shows a thinner hypodermis 

 above, bearing scattered 

 scales, and a thicker hypo- 

 dermis below, bearing the 

 dense tarsal brushes. Within 



*...-.. -V-'-r.- '--^:*\ *.,,. ."^i. * - .< :if,->VV> -.. "j^ 



C 



are seen disintegrating fat 



FIG. 7. The tarsus in the pupal stage. A, longitu- 

 dinal section of the tarsus in an old pupa. B, part 

 of another section from the same series passing 

 through one of the brushes of the 3d segment ; iu, 

 the scales constituting the brush ; v, the edge of one 

 of the brushes belonging to the third segment ; the 

 tendon which retracts the claw is drawn in solid 

 black ; n, neuroblasts. C, a bit of a section through 

 the tarsal brush in a young pupa, to show the origin 

 of the scales; w, the scales; /;, hypodermi-s ; in. 

 basement membrane: n, neuroblasts (undifferen- 

 tiated); /, fat. 



cells, and other growing 

 cells, angular and with large 

 nuclei, which I take to be 

 neuroblasts. Fig. 7, C, is 

 from a younger pupa. It shows well the manner of develop- 

 ment of the tarsal brush. The mother-cells of its constituent 

 scales settle below the general level of the hypodermis; owing 

 to close crowding, their nuclei take on a cuneate form, and on 

 the inner side of each a minute but distinct vacuole appears. 

 At this age the hypoderm cells generally, as here, reach their 

 basement membrane by long, peaked internal processes. Against 

 this basement membrane here lie heaped embryonic cells, which 

 later differentiate as the above-mentioned neuroblasts. Subse- 



