LIFE HISTORY OF DESMOGNATHUS FUSCA. 311 



cells and leukocytes during the larval period has already been 

 noted. As metamorphosis approaches (Plate V., 28, 29, and 30), 

 the nuclei of the Leydig cells (Ic) become shrunken and the cell 

 space is finally entirely given over to the intruding elements 

 (pgc(inv) and leu] from the deeper region. The surrounding 

 cells of the deeper epidermal layer, although increased in number 

 by mitosis so as to form practically two layers instead of one, 

 are correspondingly decreased in size and thus do not together 

 equal in thickness the former diameter of the Leydig cells. 



The thickness of the whole skin, i. e., epidermis plus corium, 

 does not become less; for coincident with the decrease in thickness 

 of the epidermis there is a formation of loose vascular corium 

 (cor.l) external to the dense corium and separating from it the 

 deeper layer of epidermal cells which are in contact with it during 

 the larval period. The formation of this loose corium is indeed 

 inaugurated in the migration of leukocytes and connective tissue 

 elements into the vacuoles of the Leydig cells and between the 

 cells of the epidermis. But it is only with the breaking up of 

 these Leydig cells in preparation for metamorphosis that these 

 elements and other similar ones come to form a definite layer, 

 and even then many of the connective tissue elements intrude 

 themselves between the epidermal cells. 



The development of integumental glands is particularly 

 characteristic of the preparation for metamorphosis. These 

 glands may be enumerated as follows: (i) General acinous glands; 

 (2) naso-labial glands; (3) orbital glands. 



The acinous gland anlagen appear during the general premeta- 

 morphic mitotic period of the epidermis (Plate V., 29 and 30). 

 They arise from the deeper layer of the epidermis and may first 

 be distinguished as little groups of from four to eight cells with 

 large nuclei, some of which are usually in the process of mitosis 

 (ac, Plate V., 29). They are abundantly distributed over 

 practically all regions of the body, although somewhat less 

 numerous in the skin covering the appendages. They rapidly 

 increase in size and assume the form of hollow spherical acini, 

 each with a definite lumen which opens to the exterior by a 

 narrow duct (Plate V., 30). The bodies of the glands intrude 

 into the loose corium and thus lie below the level of the epidermis, 



