The Cutaneous Glands of Common Toads. 357 



develop quickly into small mature glands, i. e., glands filled with 

 granular secretion and lined with naked, epithelial nuclei. Likewise 

 the gland buds that arise in the epidermis of the adult develop when 

 needed into small mature glands. With the growth of the glands, 

 the future production and increase of the secretion is due to the di- 

 vision of the naked, epithelical nuclei, increase in their size and 

 continued activity of the same. The globules and the liquid part of 

 the secretion are both produced by the same nuclei. 



9. The expulsion of the secretion is accomplished by the contrac- 

 tion of the smooth muscle fibers in the walls of the individual gland 

 sacs. The contraction serves the double purpose of opening the duct 

 by pulling on the radially arranged cells of the outlet, and of con- 

 certed pressure on the secretion of the lumen. The expulsion is not 

 due to the action of the subcutaneous muscles. 



10. When a wart has been stimulated to exhaustion, with few ex- 

 ceptions all the gland sacs are completely emptied and most of them 

 have collapsed. Contrary to the statement of one writer that the 

 glands of the toad refill in 24 to 36 hours, I have found that at the 

 end of seven days there is no evidence of refilling. Such gland sacs 

 degenerate arid are replaced by younger ones. With the degeneration 

 of a few or most of the mature glands of a parotid, for example, 

 and their replacement, the type of the wart changes, i. e., younger 

 glands become transitional in form, new ones arise, and there is 

 considerable irregularity in the size and shape of the new mature sacs. 



11. The mature glands of the toad are not replaced by the develop- 

 ment and ingrowth of a bud situated in the neck of the old glands, and 

 which has been said by some writers on other Batrachians to have 

 remained latent, ready for development as soon as the pressure of 

 the old gland is removed. Neither are there small glands definitely 

 arranged ahout the neck of the gland for its ultimate replacement. 



12. Glands reach maturity both in the ventral and dorsal skin. 

 They reach the mature stage in much greater numbers, on the dorsal 

 surface, where they develop to enormous sizes, and where they are 

 often closely grouped, producing warts. 



13. The pair of parotids is the greatest accumulation of glands. 

 Their position and relative size are constant for the species. All the 



