STUDIES FROM THE NEUROLOGICAL LABORA- 

 TORY OF DENISON UNIVERSITY. 



VIII. Glands and Nerve-Endings in the Skin of the Tad- 

 pole, with Plate I. 



By J. H. Massie, A.B., 



Fellow in Physiological Psychology. 



The skin of the full-grown tadpole is made up of two layers, 

 the cuticle, or epidermis, and the cutis vera, or corium. Its 

 development may be divided into three stages, arranged as fol- 

 lows: 



First, the early embryonic period, before the layers of the 

 skin have become well differentiated from the primitive mass of 

 ectoderm. 



The second stage is marked by the subdivision of the epi- 

 dermis into a columnar Malphigian layer and an outer horny 

 layer of thick-walled, much flattened cells and the appearance 

 of a narrow band of corium. 



The third stage begins when the tadpole is about 3 cm. 

 long and extends to the metamorphosis. The cells of the Mal- 

 phigian layer at the initiation of this stage begin to enlarge, 

 elongate and differentiate into two groups. In each group the 

 cells are triangular and in all cases the nucleus of the cell is at 

 the base of the triangle. In the one case the bases of the cells 

 lie adjacent to the corium, in the other, to the horny layer. 

 (Plate I, Fig. 4.) Each group, then, presents a serrated front 

 to the other; and, as the cells alternate with perfect regularity, 

 the salient angles of the one fit into the reentrant angles of the 

 other. During the process of hardening the various layers of 

 the skin often shrink away from each other, and not infrequent- 

 ly the two elements in the Malphigian layer are separated, one 

 adhering to the horny layer, the other to the corium. For 

 convenience we shall call the cells of the Malphigian layer whose 



