The Cutaneous Glands of Commen Toads. 345 



is in connection with the pad of cells. Furthermore, that the duct 

 is usually closed at several points, especially in the base of the collar, 

 against which the secretion presses. As the smooth muscle fibers 

 contract, the cells of both zones of the outlet are drawn apart, and 

 the duct is thus opened. Pressure is exerted on the periphery of the 

 lumen, causing the secretion nearest the duct to escape first. As the 

 effect of continued contraction, a large gland may be entirely emptied. 



Stages of the Gtand other than the Mature. 



Developing stages. Glands younger than the mature cannot be 

 classified into distinct types. It is safe to say that no two glands 

 are alike in every way. The degree of development is the prin- 

 cipal reason for the great variation. But among other things that 

 may modify the shape, and relative size and development of the 

 glands, is the region in which a gland may occur, whether in the 

 ventral skin, in the ordinary skin of the back, or in the parotids or 

 other warts. 



I shall accompany the general description of the glands of the 

 outer and transitional batteries with descriptions of specific glands, 

 which represent certain stages in the development toward the mature 

 glands. These have been chosen from the parotids, with the exception 

 of the first stage (Fig. 26), which was in the ordinary skin near 

 the parotid. The stages of the outer battery (I) may be divided into 

 those that are not differentiated into neck, collar and acinus (a 

 and b), and those that are (c, d, e). The latter condition is also 

 true of the glands constituting the transitional battery (II), of which 

 I shall describe but three stages (f, g, h). 



I. (a) The youngest stage which I found in the adult toad is a 

 bud, consisting of a group of cells contained in the epidermis, and 

 producing a slight bulging toward the cutis (Fig. 26). 



(b) Slightly more advanced is a mass of cells which has partly 

 pushed into the cutis. The cells forming the connection between 

 the mass and the epidermis are slightly modified (Fig. 2Y). 



Later developmental stages show all the essential parts of the 

 mature type. The acinus of the glands of the outer battery is 

 spherical or somewhat compressed at the poles. The walls of the 



