The Cutuucous Glands of Common Toads. 351 



ill the epidermis of the adult (Figs. 26-42). I will speak briefly 

 of the stages through which a mature gland of the adult has gone, 

 that has arisen as one of the first buds of the tadpole. The bud arises 

 in the epidermis and pushes into the cutis as an undifferentiated 

 gland (Fig. 10-a). A later stage is the formation of a definite 

 acinus with a lumen which is lined by uniform cubical epithelium 

 (Fig. 10-b). Soon certain epithelial cells enlarge (Fig. 10c) and 

 finally, small glands with the lumen comj)letely filled with granular 

 secretion and lined by epithelial nuclei, result (Fig. 10-d). In the 

 small toad which has just completed metamorphosis (Fig. 7), such 

 a gland is no larger than certain epithelial cells that may occur in 

 the mature gland of the adult (Fig. 52). If the reader will take 

 into consideration the difi^erence in magnification, reference to a 

 few photographs will illustrate the gradual change in the mature 

 gland with the growth of the animal. Fig. 10 represents the condi- 

 tion in the earliest transformed toad (Fig. 7). Fig. 11 represents 

 the parotid region of a small toad of the first summer (Fig. 8) ; 

 Fig. 12, the parotid of a toad of the Jate fall or after the first 

 hibernation (Fig. 9) ; Figs. 13, 22, 43 and 46, the parotid of a toad 

 of the second year, and Figs. 14, 23, 24, 44, 45 and 47, the parotid 

 of an adult toad. A comparison of Figs. 43 and 46 with Figs. 44, 

 45 and 47 shows that the naked epithelial nuclei increase in size. 

 Schultz states that he observed many mitotic figures among the 

 epithelial nuclei of the poison glands, as he called them. I have 

 never observed epithelial nuclei in a state of division, but it is 

 evident from the constant growth of a gland that division, either 

 direct or indirect, must take place. Moreover, it is probable that 

 the naked nuclei, which were left attached to the matrix, when the 

 body of the cells became secretion, continue to produce secretion 

 during the life of the gland. It would be difiicult otherwise to 

 account for the large amount of secretion in the lumen of the large 

 glands as compared to the secreting surface. Thus we see that 

 in all probability three conditions — nuclear division, increase in 

 the size of nuclei, and continued activity of the same — combine in 

 the production and increase of the secretion. 



I have said that epithelial cells occur only occasionally in the 



