VOCAL ORGANS OF MAMMALS. 569 
while the female is fawn-colored : male antelopes are blacker 
than the female. The Banteng: bull is almost black, while 
the cow is of a bright dun. Among the lemurs the male of 
Lemur macaco is coal-black, while the female is reddish yel- 
low. The sexes of monkeys differ much in coloration. Cer- 
tain male seals, bats, rats, and squirrels have brighter colors 
than in the opposite sex. On the other hand, the female 
Rhesus monkey is adorned with a brilliant red naked ring 
around the tail; this is wanting in the male, which, how- 
ever, is larger, with larger canines, more bushy whiskers 
and eyebrows ; and Darwin states that in monkeys the males 
usually differ from the females in ‘‘ the development of the 
beard, whiskers, and mane.”’ 
The vocal organs of mammals are, in general, constructed 
on the same type. The larynx is formed by a modification 
of the uppermost ring of the trachea, called the cricoid car- 
tilage, to the anterior and dorsal edges of which two arytenoid 
cartilages are attached, while a V-shaped thyroid cartilage, 
open behind, is attached to its side. The vocal cords, which 
are modified folds of the mucous membrane lining the 
trachea, are stretched between the arytenoid and thyroid 
cartilages, the slit between them being called the glottis, 
which is covered by the epiglottis. Thus, in mammals the 
organs of voice are situated almost solely at the upper end 
of the trachea. In the whales the vocal chords are not de- 
veloped. The male gorilla, which has an exceedingly loud 
voice, as well as the adult male orang and the gibbon, is 
provided with a laryngeal sac. In the howling monkey 
(Mycetes) of Brazil, the hyoid apparatus and larynx are re- 
markably modified, the body of the former being changed 
into a large bony drum or air-sac communicating with the 
larynx. The vocal organs are a third larger in the males 
than in the females. ‘‘ The males begin the dreadful con- 
cert, in which the females, with their less powerful voices, 
sometimes join, and which is often continued during many 
hours’? (Darwin). They apparently howl, as birds sing, 
for the simple pleasure of the thing. Apparently, the most 
musical mammal, man excepted, is a gibbon (Hylobates 
agilis), which can sing ‘‘a complete and correct octave of 
