TRANSFORMISM 213 



doubt that the sequences indicated by palaeontology 

 are very incomplete : they are obscured and shortened 

 by many conditions. The earlier embryologists enter- 

 tained hopes that the study of embryology would 

 reveal the direction of the evolutionary process in 

 many groups of animals : if the organism repeats in 

 its ontogeny the series of stages through which it 

 passed in its phylogenetic development, then a close 

 study of the embryological process ought to disclose 

 these stages. Although these hopes have not been 

 realised, there is yet sufficient truth in the doctrine of 

 recapitulation to enable us to state that there is a 

 rough parallelism between the palaeontological and 

 embryological sequences. 



We therefore state a plausible hypothesis when we 

 assert that different species may be related to each 

 other in the same way that the individuals of the same 

 species are related, that is, by a tie of blood-relation- 

 ship ; and that different genera, families, orders, and so 

 on are also so related. Morphological studies enable 

 us to arrange numbers of species in such a way 

 that series, in each of which there is an increasing 

 specialisation of structure, are formed. Both palae- 

 ontology and embryology show, to some extent at least, 

 that these stages of ever-increasing specialisation of 

 structure occurred one after the other. Now, stated 

 briefly and baldly as we have put it, this argument 

 may not appear to the general reader to possess much 

 force, but it is almost impossible to over-state the 

 strength of the appeal which it makes to the student 

 of biology. To such a one a belief in a process of 

 transformism will appear to be inseparable from a 

 reasoned description of the facts of the science. 



But it would be no more than a belief, not even 

 a hypothesis, if we did not attempt to verify it experi- 



