THE SEMI-APES, 255 
dwarf sloths (Bradypoda), and of the extinct unwieldy 
grant sloths (Gravigrada). The enormous fossil remains 
of these colossal herbivora suggest that the whole legion 
is becoming extinct, and that the Edentata of the present 
day are but a poor remnant of the mighty order of the 
diluvial period. The close relations between the still 
living South American Edentata and the extinct gigantic 
forms which are found beside the latter on the same part of 
the globe, made such an impression upon Darwin on his 
first visit to South America, that they even then suggested 
to him the fundamental idea of the Theory of Descent. (See 
above, vol.i. p. 134). But it is precisely the genealogy of this 
legion which is most difficult. The Edentata are perhaps 
nothing but a peculiarly developed lateral branch of the 
Ungulata; but it may also be that their root lies in quite 
another direction. 
We now leave the first main group of Placental animals, 
the Indeciduata, and turn to the second main group, 
namely, the Deciduata, or animals with decidua, which are 
distinguished from the former by possessing a deciduous 
membrane, or decidua, during their embryonal life. We 
here meet with a very remarkable small group of animals, 
for the most part extinct, and which probably were the 
old tertiary (or eocene) ancestors of man. These are the 
Semi-apes, or Lemurs (Prosimiz); these curious animals 
are probably the but little changed descendants of the 
primeval group of Placentalia which we have to consider 
as the common primary form of all Deciduata. They have 
hitherto been classed together in the same order with Apes 
which Blumenbach called Quadrumana (four-handed). How- 
ever, I regard them as entirely distinct from these, not 
