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540 A. B. DAWSON 
He concludes that the glands of batrachians have an ectodermal 
origin and that, although they come to lie within the dermis, 
they are never completely separated from the epidermis. Tar- 
chetti (04) also finds that in the regenerating tail of Triton the 
glands develop in this way, and Muhse (’09) states that in the 
adult toad new glands are continually being differentiated from 
the epidermis. 
While there is a general agreement regarding the origin of 
the glands, there is considerable diversity of opinion regarding 
their later development and differentiation. Engelmann (’72), 
Seeck (91), Schultz (89), Heidenhain (’93 a), and Nicoglu (’93) 
hold that the mucous and poison glands have an entirely separate 
development and that there is no relation between mucous cells 
and poison cells. Ancel (’02), however, states: ‘‘Les petites 
et les grosses glandes de la Salamandre ont un développement 
absolument semblable. Les glandes 4 venin ou grosses glandes 
représentent des organes plus parfaitement differencies que les 
petites glandes vers une adaptation fonctionnelle speciale.”’ 
Fano (’03) is of the opinion that in Triton the mucous glands 
of other authors are but rejuvenating stages of the poison glands, 
and Esterly (’04) is inclined to explain the conditions in Plethodon 
in a similar way. In Salamandra maculosa Nirenstein (’08) 
finds that the poison glands are developed from three sources: 
indifferent young glands, mature slime glands, and small reserve 
glands (‘Ersatzdriisen’ of Drasch, 794). Weiss (’08, 715) also 
holds that in frog tadpoles the granular glands are but meta- 
morphosed mucous glands, and Wenig (713) confirms his con- 
clusion for the Anura, as he finds that in Bufo vulgaris the 
poison glands arise as modifications of the mucous glands. 
b. Early stages in Necturus. In Necturus, according to 
Eycleshymer and Wilson (710), the fundaments of the skin glands 
first make their appearance in the epidermis of the middorsal 
region of a 32-mm. embryo. In a 36-mm. embryo the glands 
are larger, are sunk below the level of the epidermis, and possess 
alumen. In a 37-mm. embryo young glands are present on the 
sides and in the ventral region, both anteriorly and posteriorly. 
For larvae 43 mm. long, they describe the condition thus: “‘Mu- 
