LIFE HISTORY OF DESMOGNATHUS FUSCA. 303 



ably smaller. The nuclei of the cells of both layers appear in 

 many cases irregular in form and often show sharp constrictions 

 which suggest amitotic division, a suspicion further confirmed by 

 the increasing number of multinucleate cells which, in spite of 

 the absence of mitotic phenomena, appear in the outer layer of 

 the epidermis, particularly in the latter part of the larval period. 

 As the Leydig cells become larger with the continuance of larval 

 life, some of the surrounding cells of the deeper layer become 

 crowded together into a columnar form, while others appear to 

 be pushed out of line, some lying in the deeper region of the 

 epidermis and others becoming crowded into the angles between 

 the bases of the cells of the outer layer (Plate V., 29). Thus 

 the number of cells which reach from the deeper layer into the 

 outer layer becomes increased. These, however, seem not to 

 actually belong to the external layer since, even if they reach the 

 surface, they apparently do not acquire a cuticular border. 

 These slight changes in the epidermis are accompanied by a 

 gradual increase in the thickness of the dense corium, from w r hich, 

 moreover, connective tissue cells gradually invade the epidermis. 

 These together with leukocytes and branches of nerve fibers 

 may thus be seen among the cells of the deeper layer, and not 

 infrequently these invaders, as well as the pigment cells, actually 

 break through the thin membrane of the Leydig cells, and lie 

 within the large vacuolated spaces which these afford. 



The acinous glands (Fig. 15), which have already developed 

 and begun to function at the time of hatching, remain in a fully 



group of glands of a terrestrial larva; (c) vertical section through one of the glands 

 of the supra-branchial group of an aquatic larva in late spring, hence near the end 

 of the larval period; (d) vertical section through one of the supra-branchial group of 

 an aquatic larva in February, showing an almost completely discharged condition 

 induced by prolonged mechanical stimulation immediately before the specimen 

 was killed; (e) vertical section through one of the supra-branchial group of an in- 

 dividual immediately after metamorphosis, showing the gland in an empty con- 

 dition and undergoing atrophy, while in the Icose corium nearby are seen two of 

 the newly developed acinous glands of the adult period of life. Note the position 

 of the larval gland below the level of the dense corium, while the adult glands are 

 in their permanent location external to this layer. 



Agl, adult gland; cap, capsule of the gland; cod, dense corium; col, loose corium; 

 du, duct of the gland; ep, epidermis; gc, giant cells of the gland; Im, lumen of the 

 gland; pc, pigment cell which has invaded the gland; sc, secretion discharged from 

 the gland. Drawn with Abbe camera. X 225. 



