304 INEZ WHIPPLE WILDER. 



active condition throughout larval life. These glands, arranged as 

 above described (cf. p. 291 Vol. XXIV. Biol. Bull.), lie quite below 

 the dense corium, embedded in the subcutaneous connective tissue, 

 and communicating with the external surface by means of a narrow 

 duct. Although of the type of amphibian gland variously design- 

 ated as "granular" or " poison," they do not in detail correspond in 

 all respects to the descriptions of such glands in other amphibians. 

 They vary greatly in size, the largest when in a distended con- 

 dition having a diameter eight times the thickness of the skin, 

 while the smallest when distended have a diameter only twice 

 the thickness of the skin. They are spherical or subspherical 

 in external form; the larger ones, especially those of the supra- 

 branchial group, are not of the simple acinous type which this 

 external form suggests, however, since internally the lumen is 

 partially subdivided by invaginations of the single layer of gland 

 cells, as well as by the occurrence here and there of groups of 

 these cells which are much taller than the rest and thus encroach 

 upon the lumen. The connective tissue sheath (cap) of the gland 

 follows closely the invaginations. The glands of all sizes are 

 particularly characterized by the development of certain cells 

 into the "giant" type (gc) through an enormous accumulation of 

 granules of the same sort apparently as those which fill the other 

 cells of the gland. These giant cells are differentiated very early 

 in the development of the glands, even while mitosis is still in 

 progress and before the lumen of the gland has appeared; in all 

 of the glands they comprise at least one group of some eight or 

 ten cells which lie near the orifice of the gland upon one side and 

 become almost completely surrounded and cut off from the rest 

 of the gland by the ingrowth of the connective tissue sheath 

 (Fig. 15, b). Thus placed they form a mass nearly equal in 

 volume to half of the whole gland, so that a section through the 

 middle of the gland parallel with the external surface of the skin 

 often shows the remainder of the gland wrapped in a crescentic 

 form about this mass of giant cells. Giant cells occur also in 

 other parts of the larger glands, either as isolated cells or in small 

 groups of two or three. The granules filling all of the gland cells 

 are similar, except that those in the giant cells become much 

 larger. The ordinary cells, however, appear to constantly dis- 



