The Cutaneous Glands of Common Toads. 333 



Calmels is the only one of this group who has dealt with the toad. 

 He has evidently excluded from his discussion the glands of the 

 ventral surface, for he makes the statement that the poison glands 

 which occur, only on the dorsal surface differ from those of the ventral 

 side, in that they contain a milky secretion produced by the poison 

 cells. He makes no mention of smooth muscle fibers about the glands. 

 It is evident from his description that he has seen the muscle fibers, 

 but has mistaken them for epithelial cells. Recognizing but one kind 

 of gland, he establishes with the epithelium as a basis four types. 

 According to him, the youngest epithelium is found about the lumen 

 of the largest glands, but he has mistaken the muscle fibers in slightly 

 longitudinal view for young epithelium. What he describes as 

 daughter cells of the epithelium in the other, three stages of epithelium 

 found in the small glands are probably the transverse view of muscle 

 fibers. I have not had access to Leydig's article nor to Nicoglu's. 

 JSTicoglu and Vollmer are referred to by Esterly as having stated 

 that they saw regenerating forms of glands. Both worked on sala- 

 manders. Vollmer figures a small gland arising from the epidermis, 

 but does not give intermediate forms. His study was largely an 

 experimental one. I^icoglu and Heidenhain each seem to have pub- 

 lished an article in 1893, as the results of the same investigation. 

 If this is correct, the two reached different conclusions, for Heiden- 

 hain divides glands into three kinds — mucus, poison and double. 

 Esterly refers to Nicoglu as an investigator who believed in one kind 

 of gland. 



Junius, dealing with the structure of the cutaneous glands of the 

 frog, describes what he believes to be the young and old forms. 

 He, however, merely expresses it as a belief that the forjns he de- 

 scribes are developmental stages of the same kind of gland. He did 

 not observe intermediate stages. He further expresses it as his 

 opinion that in the renewal of glands, the process of their embryonic 

 development is probably, repeated. He offers no evidence for this 

 opinion. 



Ancel deals with the development of cutaneous glands especially 

 in the salamanders. He states that all glands arise in the epidermis, 

 but that certain among them are arrested sooner in their evolution 



