17 W. L. TOWER. 



These glands arise in the embryo and in later larval stages 

 through the modification of the hypodermal cells. In Fig. 2 are 

 shown five stages in the development of these glands. 



The first stage in the development of one of these glands in 

 larval life is usually found in the latter portion of the period of 

 maximum nutrition and shows the nucleus greatly enlarged, the 

 chromatin greatly increased in amount and scattered, with the 



FIG. I. L. efecim/ineata. Section of pronotum of larva about to pupate, in early 

 stage of exuviation, showing large number of exuvial glands, g. C / , cuticula of larva 

 being removed ; C 3 , developing new cuticula ; H, hypodermis ; /, fat body ; /, 

 muscles ; /, trachea. 



cytoplasm seen (Fig. 2). In the period of differentiation thisd 

 cell grows very rapidly projecting inward below the hypodermis, 

 but retaining a delicate connection with the cuticula (Fig. 2, B}. 

 The cell remains in this condition through the following ecdysis 

 and appears after ecdysis unchanged, excepting that the gland 

 now has a delicate duct leading to the surface, this being devel- 

 oped as the result of the glands not forming chitin at this point 

 of attachment to the outer surface of the hypodermis (Fig. 2, C), 

 During the last larval stage the character of these glands, especi- 

 ally in the periods of differentiation and preparation, change rap- 

 idly (Fig. 2, D and E), becoming first larger, the nucleus and 

 chromatin growing immensely in size and quantity, the cyto- 

 plasm remaining dense and slightly vacuolated. At the begin- 



