32 THE INTERNATIONAL MONTHLY 
original documents, which bear evidence of their true dates and of 
their order of succession, and, however incomplete they may be, 
they have not been falsified by late interpolations and forgeries. 
If the analogue of Grimm's law is to be found anywhere in the 
animal kingdom, it will surely be deduced from a study of these 
well-defined genealogical series of fossils. Indeed, a number of 
paragraphs of such a law may already be so deduced. It is true, 
these paragraphs have not yet found general acceptance among 
zoologists, but that is because very many zoologists ignore palae- 
ontology and seem to think that it has nothing of importance to 
offer them. 
It would not be worth while, even if the limitations of space 
permitted, to consider all the deductions as to modes of evolution- 
ary change which have been suggested by the study of genealogi- 
cal series of fossils, but two or three principles should be men- 
tioned which are of especial importance, and which are established 
to a very high degree of probability. 
(1) Evolution is ordinarily a continuous process of change 
by means of small gradations, which sometimes require a vast 
period of time to secure a relatively small advance. This does 
not imply that the rate of change was always uniform, — it 
probably was not, — or that a sudden alteration in the conditions 
of the environment may not bring about a discontinuous, or 
u per s altum" development. It means that the usual and nor- 
mal mode of advance is by continuous, small changes. 
(2) Evolution is, in most instances, direct and unswerving. The 
rise of new forms and the decadence of old ones usually take place 
by relatively straight paths, not in zigzag or meandering lines. 
Indeed, on looking over a long series of fossils, it is often difficult 
to resist the somewhat fantastic belief that the animals were mak- 
ing for a consciously selected goal, so steadily do the successive 
members of the series keep to the prescribed path. A path once 
taken may, of course, be diverged from, but in that case the origi- 
nal path is not regained. This steadiness of development is a 
general truth, applicable to the organism as a whole ; in minor 
details of structure more latitude of variation seems to be admissible. 
