232 University of California Publications. [zoology 



In addition to the funnel cells proper. Nicoglu lias described the 

 arrangement of the cells in the epidermis which are to replace 

 the funnel cells as they are thrown off at the time of moulting. 

 The same condition is found in Plethodon and does not differ at 

 all from that in Triton (Nicoglu '03) or in Salamandra (Ancel 

 '02). (PI. XX. Fig. 4: PI. XXIII, Figs. 27, 28, 29, 30. rep. c.) 



As further evidence that the cells described as replacement 

 cells really have that function, Plethodon shows that the lower 

 ends of the replacement cells, especially those nearest the duet, 

 extend inward as do the prolongations of the funnel cells. (PI. 

 XXIII, Fig. 27. rep. c.) The arrangement of the former very 

 strongly suggests that they are of the same nature and function 

 as the funnel cells. And in cross sections of the duets the 

 replacement cells are shown rolled one within the other as in 

 PI. XX. Fi-. 4 : pi. XXI, Fig. 16. rep. c. The cell first to 

 replace the one thrown off at moulting immediately surrounds 

 the duct; the cell next to replace this one lies concentrically out- 

 side it, and so on. In Mallory's stain the cell boundaries are 

 very distinct, and there can be no doubt of the structure as 

 described either in cross or in longitudinal section of the ducts. 



The walls of the gland sacs proper are composed, in many 

 Amphibia, of a number of elements which have been described 

 and all of which need not lie discussed at length here. In the 

 most peripheral layer are connective tissue and elastic fibrils, as 

 is shown by the use of Mallory's connective tissse stain for the 

 former and orcein for the latter. Nerves, lying in this layer, also 

 extend over the gland. Inside the connective tissue sheath, as 

 it is generally called, lie the muscle fibres, and next to them the 

 epithelium of the gland. 



(See in this connection Drasch '92, '94; Eberth '09; Eck- 

 hard '49; Englemann '72; Ileusche '56; Ley-dig "7(i. n. b; 

 Paulieki '85; Phisalix-Picot '00; Schuberg '03; Schultz '89; 

 Seeck '91; Stieda '65; Tonkoff '00; Wiedersheim '86.) 



Because of the intimate relation between the connective 

 tissues of the gland wall and those of the corium, it is necessary 

 to consider in more detail the structures of the inner, middle 

 and outer layers of the corium. Schuberg ('03) has studied the 

 corium of Axolotl most minutely. I have continued his results 



