PLATE 4 



KXPLANATION OF FKUaiKS 



2;] From a pupa slightly older than that of figure 22. Histogenesis has pro- 

 gressed somewhat furtlier. Note the cut ends of fibrillae in the longitudinal mus- 

 cles {l.m.). 



24 A stitge yet more advanced in the histogenesis of the imaginal muscles. 



2o Note the forming fibrillae in the circular and longitudinal muscles. The 

 muscles arc now arranged in their two definite layers and the e])ithelium is now 

 reformed. From an older pupa. 



2() Cross striations can now be observed in the newly re-formed circular nuiscles 

 {(■..III.). These striations are faint and remain so till the emergence of the atlult. 

 g.iiL., granular mass occupying the space between the loosened intima and the 

 euiThelium. From a pupa ICO hours old. 



27 This figure shows the characteristic method of cell division; m, dividing 

 cell; si., strand connecting the cell with the basement membrane; b.m.^ note the 

 distinct basement membrane between the epithelium and the muscular layer. 



28 Shows a condition similar to figure 27. 



2!) The epithelium from a i)upa forty-eight hours old; r, row of black dots near 

 the outer ends of the epithelial cells where the imaginal intima will be re-formed. 



()22 



