and on Scales in Mammals. 9 
of other species of Macropus, which use their tails in a pre- 
cisely similar fashion, scales are wanting. What advantage 
does the short tail of Perameles doreyanus derive from its 
well-developed coat of scales, while the similarly constituted 
tails of Perameles Gunni and P. obesula are scaleless? ‘The 
species of Phalanger with a typical prehensile tail are without 
a coat of scales, and the same applies to the prehensile tails 
of monkeys. ‘The arboreal Sciuride, too, have scaleless tails. 
The large rows of scales on the ventral surface of the root of 
the tail of the Anomaluride are a specialization and a further 
development from small scales, which cover the entire tail. 
Moreover, what is the nature of the adaptation that causes 
the extremities of many Marsupialia, Rodentia, and especially 
Insectivora to bear scales or indications of such ? 
The foregoing examples clearly illustrate the irregularity 
of the occurrence of scales even in the case of most closely 
allied species, as well as their independence of the mode of 
life of the animals. They become intelligible when we con- 
sider them from the point of view that scales are rudimentary 
structures, which have persisted in different degrees or in 
part already disappeared, and only in altogether isolated 
cases underwent further development in a specialized form 
(Manide, Dasypodide, Castor, Anomalurus). Romer, on 
the contrary, considers that the scales ‘‘ are secondary pheno- 
mena of adaptation, which were acquired by true hair-bearing 
animals, since they were more advantageous to them for their 
mode of life, e. g. for the tail as a prehensile and supporting 
organ, than the less firm coat of hair.” 
On the other hand, Rémer justly ascribes to me the view, 
that I held it to be improbable that the scales had developed 
as structures entirely new and without an inherited basis. 
In opposition to this Rémer observes, “ The inherited basis 
is, however, supplied in the wonderful capacity for differen- 
tiation possessed by the skin, which is indeed to be found in 
all groups of animals.” What the respected author meant 
to convey by this somewhat formal paraphrase of the fact 
that the mammalian integument can actually produce scales, 
I was unable to quite understand. I found the greater diffi- 
culty in doing so since he goes on to state that “ the scale- 
like coverings of Mammals, which develop in consequence of 
a capacity of the integument inherited from the Reptiles, and 
so to a certain extent are to be regarded as a case of ‘throwing- 
back,’ justify the conclusion that such a covering was 
formerly of general occurrence and clothed the entire body, or 
at least the dorsal parts thereof.” 
How great the agreement between us is may be gathered 
