636 Distribution of Colour in Reptiles , &c. [November 
to long stripes, spots, and transverse bands. The longitu- 
dinal stripes are here also the pristine pattern from which 
spots and transverse bands proceed in turn, whilst as the 
ultimate stage the pattern disappears and the animal be- 
comes concolorous. The mammalian fauna was originally 
striped, whilst spotty and tigrated forms appeared in suc- 
cession, the same changes of design appearing in the same 
order of succession. Sometimes there appear only transitory 
intimations of the earlier types ; the last is sometimes 
wanting; sometimes the intermediate also, and some- 
times all. 
The laws of male preponderance, and of the undulatory 
propagation of development from behind forwards, have not 
been so distinctly traced as in birds and reptiles. But a 
progressive development from below upwards is shown in 
this manner, that the longitudinal design persists longest in 
the median line of the back, often as a single stripe, whilst 
lower down it is resolved into spots or even transformed 
into bands. 
In Mammalia, as well as in other animals, the trans- 
formation of the designs takes place according to fixed laws. 
Not even the most insignificant spot on the body is without 
genetic or phylogenetic signification. The persistence of 
the heredity of such marks is extraordinary, and thus here 
also the design appears a most important means for recog- 
nising the affinity of forms, and for a scientific classification. 
For further details we must refer our readers to the 
“ Jahreshefte des Vereins fur Naturkunde in Wiirtemberg ” 
(vol. xxxix., 1883, P« 5b). 
From the uniformities which he has recognised,— accord- 
ing to which the transformation of patterns proceeds, even 
to the minutest detail, — and from the circumstance that 
in numberless cases animals and plants produce formations 
in which the principle of utility can have had no immediate 
effedt, but whose origin may be compared with that of crys- 
tals, Herr Eimer concludes that the essential principle of 
the conversion of forms is a development depending upon 
constitutional causes, and proceeding of necessity in a cer- 
tain direction. The principle of utility, though important, 
is merely a modifying fadtor. The origin of new species 
depends, according to Eimer, upon the arrest of forms in 
various stages of this natural development. 
