1882.] Animals and their Diet . 581 
which is first traced in the Eocene Tertiaries, is character- 
ised by its complicated and highly specialised digestive 
organs, evidently modified from the normal mammalian 
type, so as to be adapted to a purely vegetable diet. This 
same structure, or at least one highly similar, is met with 
again among the sloths, the only phytophagous section 
of the Edentata. 
The next consideration is that numerous animals which 
are zoophagous at one epoch of their life may be phytopha- 
gous at another, whether earlier or later. This change is 
not accidental or compulsatory, but ensues naturally and 
normally in every individual of the species in question. 
Thus all mammalian animals, whatever may be their future 
diet, begin life as zoophagous beings so long as they are 
nourished on their mother’s milk. Indeed it is fully proved 
that, e.g., the human infant is for some time incapable of 
digesting vegetable matter. 
Among birds we meet with the same faCt. Setting aside 
the many groups which are zoophagous throughout life, we 
find that, as a rule, the young of the seed- and fruit-eating 
species require an exclusively animal diet, consisting of 
inserts, worms, &c. In other cases they are fed with half- 
digested food disgorged from the crop of their parents. 
There are few, if any, cases where a bird when just hatched 
is able to feed on crude vegetable matter. 
Among inseCts many similar changes take place. The 
robber-flies of the genus Brax , which in their adult state 
destroy numbers of hive-bees, feed when larvae upon vege- 
table matter. Not a few butterflies will sip the juices of 
dead animals, though in their caterpillar stage they are 
purely phytophagous. The larvae of the hive-bee are fed 
upon honey and pollen, without any accompaniment of ani- 
mal matter. But when mature they may be styled omnivo- 
rous, as, in addition to honey and juices of fruits, they are 
found to lick meat in butchers’ shops, and even, according 
to Fritz Muller, to imbibe excrementitious liquids, as do also 
the butterflies. 
Changes arising from a scarcity of food, or from caprice, 
are also on record. The two Carnivora which have become 
domesticated often partake of vegetable matter. The cat is 
even known to steal raisins and dried plums, and, according 
to Mr. Bates, in Brazil it goes into the woods to eat the 
fruit of the Tucuma palm. But amongst wild animals a 
change of diet when it occurs is almost invariably in the 
opposite direction, i.e., from vegetable to animal matter. 
Under this head must figure the well-known case of the 
