LIMITS OF HEREDITARY CONTROL 861 
a large sample of the species. Without this data one would 
scarcely be in a position to appreciate the degree of resemblance 
or difference that exist among the foetuses of the different sets. 
Owing to the existence of an extensive curio industry, making 
a specialty of baskets shaped from the shells of armadillos, there 
has been afforded an exceptional opportunity for gathering a large 
mass of data on the variability of the species. By availing our- 
selves of the large stocks of basket-shells in the hands of various 
dealers we have been able to examine 1768 individuals for scute 
and band ‘abnormalities’ and to count the scutes in the banded 
region of over 500 shells, including those of all males and females 
sent to us alive. 
MORPHOLOGY OF THE INTEGUMENT 
The integument is one of the most characteristic features of 
the anatomy of the armadillo. For the most part it consists of 
a series of bony plates which are arranged so closely together as 
to form an almost continuous armor, especially on the dorsal and 
lateral parts of the body. When attacked the animal is able to 
retract itself well within this shell-like structure, much after the 
manner of a turtle, and although the belly and legs do not possess 
an armor, in the strict sense of the word, yet even here the skin 
is studded with horny scutes and the feet are armed with powerful 
claws. Altogether the integument of the armadillo forms a 
protective structure of high efficiency in an otherwise defenseless 
animal. 
In our species, Tatu novemcinctum, five of the so-called armor 
shields described for armadillos are present. These are the ce- 
phalic, covering the front of the head; the scapular, overlying the 
shoulders; the thoraco-lumbar or banded region (sometimes called 
the movable zones), consisting of nine bands or incomplete rings; 
the pelvic, covering the hips; and finally the caudal shield, which 
consists of a series of rings surrounding the tail (fig. 17). 
The elements composing the armor exhibit in each of the shields 
a somewhat different and more or less characteristic arrangement; 
but since in this paper we are concerned with the study of varia- 
