396 HISTORY OF SCIENCE. 



should seize others by deeply burying its claws into their bodies, must, 

 by these repeated efforts, get claws of a size and curvature that would 

 impede its motion in walking or running over stony ground ; it has 

 come to pass in this case that the animal has been obliged to make 

 other efforts to draw back these too prominent and hooked claws by 

 which it was inconvenienced, and the result has been the formation 

 by little and little of those peculiar sheaths into which cats, tigers, lions, 

 etc., retract their claws when they are not in use." The reader will 

 hardly fail to notice how very unsatisfactory, not to say impossible, is 

 this explanation of the process by which the modification of organs was 

 brought about ; and this was doubtless the reason why these views on 

 the evolution of species attracted comparatively little attention until a 

 later period, when the fatal defect of Lamarck's theory was removed 

 by certain new views brought forward by a celebrated English naturalist 

 still living. It is because Lamarck's theory, after having slowly ac- 

 quired support and recognition from various quarters, and especially 

 after having received from Darwin's speculations increased vitality, has 

 obtained in some form a very general acceptance amongst scientific 

 naturalists, that the views of the French naturalist deserve a degree of 

 attention which they could not claim merely by their boldness and 

 originality. 



Lamarck's theory, then, regards the various species of animals as 

 produced by modifications of originally simple forms, increasing pro- 

 gressively in complexity of organization by the operation of laws which 

 have been always the same. The modifications which present them- 

 selves to us in the various forms of animal life have required for their 

 evolution a period of time to which the duration of human life, or 

 even the interval which has elapsed since the epoch of our most 

 ancient annals, may count as but a second. The changes actually in 

 progress are unperceived, by reason of their relative slowness. A sup- 

 posititious comparison will make this clear. Suppose that the duration 

 of human life extended only to a second of our actual time, and that 

 it was given to us to contemplate the face of a clock such as we now 

 possess. No individual could ever notice the motion of the hour 

 hand in the course of his own life, and even the comparison of the 

 recorded observation of sixty generations might fail to detect it ; but 

 even if some persons, by comparison of still older observations, had 

 acquired the conviction of the reality of the motion, others would not 

 share this conviction ; for seeing the hour hand stationary on the dial, 

 as their fathers before them had also seen it stationary, they would 

 declare that those who asserted its motion were mistaken in their in- 

 ferences. 



In a supplement to the "Philosophic Zooloqique" Lamarck gives a 

 table exhibiting the conjectural descent of the several sub-kingdoms 

 of animals. He thinks that the lowest part of the scale may have two 

 unconnected divisions, and that the series in series sends off branches 



