VOL. i.i Esterly. Poison Glands of Plethodvn. 233 



in general in Plethodon, and particularly as to the relation of 

 the connective tissue bundles of the inner layer of the coriura to 

 those of the middle layer. He found (p. 222) that columns of 

 connective tissue pass perpendicularly from the inner into the 

 middle layer, and seem to serve as mechanical supports for the 

 glands, since under each one such a column of tissue is found. 

 The same arrangement occurs in Plethodon except that the 

 pi'i-pendicular bundles do not stand beneath the glands, but 

 around them, as can be seen in longitudinal sections of the 

 glands. (PI. XX, Fig. 5, c.t.b.) In spaces between the large 

 glands or on the ventral side of the tail, the bundles from the 

 inner layer of the corium can be seen especially well. The con- 

 nective tissue fibres from the wall of the gland unite with the 

 outer layer of the corium which then, lying next the muscle layer 

 of the gland, passes toward the surface of the epidermis and 

 ends on the side of the neck of the gland about a third of the 

 distance between the inner and outer boundaries of the epider- 

 mis. (PI. XX, Fig. 8; PI. XXIII, Figs. 27, 31.) This appears 

 in both longitudinal and cross sections of the ducts. In the 

 latter can be seen a crescent of connective tissue on each side of the 

 duct between the muscle fibres and one of the replacement cells. 

 (PL XXIII, Figs. 28, 29; PI. XXI, Fig. 16, c.t.) Ancel ('02, PI. 

 IX, Fig. 22) seems to have shown the same in longitudinal section. 

 The elastic fibres pass through the inner layer of the corium 

 into the middle layer in company with the connective tissue 

 bundles as Schuberg ('03, p. 231) has described. The elastic 

 fibres can be followed around the glands, and over them in 

 tangential sections. The fibres are of nearly the same calibre 

 throughout and all of them take the same general direction, 

 from the inner corium layer perpendicularly or sharply turned 

 toward the outer layer. As in the case with the connective 

 tissue bundles the elastic fibres pass at once around or over the 

 large glands, and ar-e not found arranged perpendicularly beneath 

 them as in Axolotl. (Schuberg '03, p. 232, Fig. 14.) On the 

 sin-face of the gland they are branched in a few cases; usually, 

 however, only single fibres of wavy, curving and regular outline 

 are visible, ending before the outer corium is reached (Schu- 

 berg '03, PI. XXI, Fig. 9, t /./.). 



