THE GENESIS OF LIVING ORGANISMS 189 



cerned solely with the search for signs of genesis. To avoid 

 going astray through taking a sign of function for a sign of 

 genesis, morphology must call in the help of comparison. 

 Only when we have shown that, in spite of change of function, 

 the same anatomical characters persist in various genera 

 and species, can we decide with any confidence as to which 

 are signs of genesis. For instance, the fixed number of seven 

 cervical vertebrae in all mammals, whether they have a long, 

 flexible neck like the giraffe, or a short, rigid neck like the 

 whale, is undoubtedly to be taken as a sign of genesis. On 

 the other hand, the arrangement of the lamellae in the bones 

 of mammals, which changes according to the distribution of 

 the weight of the body, is a sign of function. 



There are immutable laws, according to which the shiftings 

 of the body-mosaic proceed, before the definitive form is 

 reached ; and these laws we strive to discover with the aid 

 of the signs of genesis, for it is these which tell us not only 

 about the delimitation of the genetic building-stones, but also 

 about the changes that take place in these. 



From study of the animals now living, it appears that the 

 higher animals display, as transitory stages, rudiments of 

 structures that become organs in the lower forms ; in the 

 former these do not reach complete development. 



This fact, however important it may be for the deter- 

 mination of relationship, is no more than an expression of the 

 centrifugal architecture of animals. - How else, indeed, should 

 this centrifugal architecture express itself from the germ ? 

 Surely it is just what we might expect that, when we compare 

 various kinds of animals together, the first systematic arrange- 

 ments in the mosaic should resemble one another, and then, 

 after a certain time, become differentiated from one another. 

 A continuous chain of shiftings and changes characterises the 

 development of even the highest animals ; and so we get the 

 impression that certain stages are to be explained only on the 



