LIFE HISTORY OF DESMOGXATHUS FUS( A. 287 



THE SKIN OF THE TERRESTRIAL LARVA. 



The epidermis of the newly hatched larva (Plate IV., 19, 

 20, 21, and 22) is in the typical larval amphibian condition in 

 that it consists of two layers of cells; these are for the most 

 part subspherical in shape with polygonal outlines when viewed 

 in a section parallel with the external surface. They possess 

 large nuclei which in both layers show a small precentage of 

 mitosis. The cells of the outer layer have a deeply staining 

 cuticular border on the exposed surface, forming all together a 

 continuous cuticular layer (cii) covering the external surface. 

 In general over the dorsal and dorso-lateral surfaces the outer 

 layer of the epidermis is the thinner one and its cells are slightly 

 flattened. Over the lateral and ventral surfaces the outer layer 

 is the thicker, the cells here approaching the columnar form, 

 while their nuclei are piriform with the pointed end directed 

 toward the outer surface and often nearly reaching it; in these 

 regions the inner layer is considerably thinner and the nuclei 

 smaller. Over the region which is still distended with yolk, both 

 layers are thin, the cells of the inner one approaching the squa- 

 mous type. In a few limited regions as, for example, the lateral 

 wall of the body beneath the gills, the whole epidermis is very 

 thin, and the cells of both layers decidedly of the squamous type; 

 as seen in cross section their nuclei alternate, and the whole 

 appearance may thus even simulate a single cell layer. 



Beneath the deeper layer of epidermal cells in practically all 

 regions of the body except the snout, there is a dense corium 

 which fits closely to the deeper layer of cells, thus following their 

 contour. This corium is a little thicker than the cuticular layer 

 of the outer cells and is from one eighth to one sixth as thick as 

 the whole epidermis. 



In those regions of the body which are pigmented, the dorsal 

 and lateral surfaces, the pigmentation is threefold. The ex- 

 ternal layer of epidermal cells possesses an intracellular pigmen- 

 tation in the form of a layer of pigment granules (pgg) immedi- 

 ately beneath the cuticular layer and forming a sort of cap over 

 the nucleus. In addition to this intracellular pigmentation there 

 may be seen, between the cells, delicate intercellular ramifying 

 branches (pgbr} of pigment cells (pgc) of the connective tissue 



