TEGUMENTAL ORGANS 13 
The development of mammary glands and teats is always 
initiated by a shallow depression of the integument (/.7., Fig. 9, A), 
the mammary pit; the base of this pit is the glandular area, 
and the surrounding border (v) the rampart of the gland. The 
Malpighian stratum of the epidermis at the base of the glandular 
area, by inward proliferation, gives rise to the glandular tissue. 
The mode of development of the teats is not the same for all 
SSE 
g.m. 
Fic. 10.—DISsECTIONS OF A BROODING FEMALE OF Echidna hystrix. 
A, Ventral aspect ; B, dorsal inner view. ++, The two tufts of hair, in the lateral folds of 
the mammary pouch from which the secretion flows. On each side of the pouch 
(6.m.), which is surrounded by strong muscles, a group of mammary glands (g.m.) 
opens ; c/. denotes the cloaca in each figure. (After W. Haacke.) 
Mammals. LEither (Fig. 9, B) the rampart which borders the 
depression rises and forms a tube (the lumen of which is known 
as the mammary canal), into the base of which the true ducts 
open, or (Fig. 9, C) the glandular area rises in the shape of a 
papilla, while the rampart degenerates. The latter, in which the 
nipple must be considered as a secondary formation, is exemplified 
in the Marsupials, the Lemuroidea, Apes, and Man; in the former, 
which obtains in the Carnivora, Pigs, Horses, and Ruminants, it 
is a primary formation. The first indications of the primary 
