XIV PREFACE. 



Again, we find that the comparatively low forms of 

 life in which all these developmental transitions are 

 embodied, instead of being almost unchangeable as 

 they ought to be if there were any truth in the con- 

 tradictory doctrines to which we have already referred 

 are variable in the highest degree. They pass through 

 the most diverse and astounding transformations, and, 

 as we have endeavoured to show in the Third Part of 

 this work, such organisms are often seen to be derived 

 from matrices wholly unlike themselves. 



In fact, these lower forms of life corresponding 

 pretty closely with the Protista of Prof. Haeckel form 

 an enormous and ever-growing plexus of vegetajxand 

 animal organisms, amongst which transitions from the 

 one to the other mode of growth take place with the 

 greatest ease and frequency. Here Heterogenesis is 

 constantly encountered, and variability reigns supreme,, 

 so that those assemblages of definitely recurring indi- 

 viduals, answering to what we call c species/ are not 

 to be found amongst them. They are essentially tran- 

 sitory and variable forms, which I have proposed to 

 name c Ephemeromorphs.' Regularly recurring or homo- 

 genetically produced types, both animal and vegetal, 

 are, however, constantly arising out of this great ephe- 

 meromorphic plexus, either by direct and sudden pro- 

 cesses of transformation or by some intermediate and 

 cyclical processes of so-called ' alternate generation.' 



And until such assemblages of repeating individuals 

 make their appearance that is, until Homogenesis 

 becomes the rule the c laws of heredity' can scarcely 

 be said to come into operation. Hence the complexly- 

 interrelated individuals, constituting this vast under- 



