118 A. A. W. HUBRECHT, 
has given origin to, remaining in connection with the maternal 
tissues. 
I hold this to be not a secondary modification which has 
arisen among mammals that were already frankly deciduate, 
but, on the contrary, a more primitive developmental phase. 
In very many cases it may have preceded that more complete 
arrangement in which the uterus, after having expelled the 
foetus, also rids itself (be it even at the cost of some of its own 
elements—rapidly renovated after parturition) of the growths 
(afterbirth) by which the embryo has succeeded to obtain so 
firm a hold on the maternal sanguiniferous tissues. 
If we look at the Carnivora, at the bats, the rodents, the 
Primates, and the Insectivora, we find their more complicated 
placentary structures to belong to very divergent types. Inthe 
latter order there is no common type, but a different one for 
nearly every genus. The shrew, the mole, the hedgehog, and 
the Tupaja are all most incredibly divergent with respect to 
their placentary arrangements. Only when the comparative 
investigations shall have covered a more considerable number 
of different genera, the time for new theoretical generalisations 
will have arrived. 
Towards the accumulation of material that would be thus 
available I hope the Spolia Nemoris here described may 
contribute. 
