THE LIVING WORLD. 
523 
The Colugo ( Galeopithecus volans) is not a true flyer, but can sustain itself 
in air for a short time, while passing from tree to tree. It uses its tail as a 
rudder, but perhaps more frequently flies down than up. It prefers climbing to fly¬ 
ing where it has any choice. It is generally quiet during the daylight and the 
darkness, preferring the hours claimed by Aurora, and those distinguished by 
the term crepuscular (as belonging to the twilight). Passing its life amidst 
the thick foliage of the forest trees, it lives upon leaves as one might expect, 
although it varies its fare by occasional dishes of insects. It is often classed 
among the bats and has been described in that department of The Living 
World. 
CETACEANS. 
As bats are the flying mammalia, so cetaceans are their antithetical, or 
swimming congeners, which strain from the water of the sea the smaller 
animal life which supplies them with food. Some of the Cetaceans, or Whales, 
have already been considered in connection with the fishes, since, regarded 
otherwise than structurally, the cetaceans have many external resemblances to 
the order of fishes. The sea has thus far been needed by man only as fur¬ 
nishing channels for his commerce, and as supplying the materials for certain 
industries. Hence, as should be expected, if the author’s theory and conclu¬ 
sions have seemed to be sound and well-supported, the larger forms of life 
have persisted longer in the waters than upon dry land. Still, the whales , 
narwhals, grampuses, porpoises and dolphins, are rapidly growing fewer, and 
doubtless making way for a new succession of life, which will be found better 
suited, and more directly contributive to the needs of man’s higher civilization. 
The cetaceans are protected by their bulk, strength, and thick skins against 
attacks from dangerous enemies other than man—irresistible man. Being 
mammals, and therefore requiring oxygenated air, they not only rise to the 
surface, but find their abundant blubber useful, not alone as securing buoyancy, 
but as protecting them against the inclemency of the deep sea. Regarded 
anatomically, the cetaceans rank high or low, as we regard the organism of the 
brain, or that of the skeleton. Their dentition is peculiar in that the teeth 
are not incisors, canines or molars, but special cone-like forms, suited to the 
uses to which they are to be put. The stomach of the cetacean , like that of the 
camel and other of the cud-chewing animals, is divided into chambers, and while 
the design of this structure is not certainly known, it would seem to furnish an 
illustration of the wonderful means by which all animals are adapted to the 
normal conditions of their life. The circulatory system, likewise, is specialized, 
and the veins and arteries form reservoirs, so as to provide, seemingly, for the 
frequent and long-continued descents which the cetacean makes into the deep 
sea. The cetaceans , as fossils, make their earliest appearance in the Eocene 
period, where we find the phocodontia , the squaladon , and the zeuglodon . 
These fossil-forms give evidence of having differentiated into the cetacea and 
the succeeding class, sirenia. 
The Australian Two-toothed Whale (. Ziphius australis ) is ash-colored, 
lighter above and darker below, and in connection with the Nova Zembla Two¬ 
toothed Whale ( Ziphius novcezoelandice) , the European Two-toothed Whale 
(,Ziphius cavirostris) , the Two-toothed Cow-fish (Mesoplodon bidens ), the New 
Zealand Cow-fish ( Mesoplodon grayi ), the Bottled-nose Whale ( Hyperoodon 
butzkopf ), are interesting as belonging to a species regarded, until quite recently, 
