m 



PREFA CE. 



XV 



uncha 



^^geable^ 



lying plexus of Infusorial and Cryptogamic life, must 

 remain wholly uninfluenced, so far as their form and 



1 already ,ef, 

 ihey 



structure is concerned^ 

 termed ' Natural Selectic 



what Mr. Darwin has 

 Such vegetal and animal 



Third 



organisms, however, gradually tend to become more and 

 ^^forrnlt''' '"'" "^°^^ complex. An ascending development takes place, 



^^^■' and as this occurs, the causes which originally sufficed 



to determine their form and structure, and which for a 

 ° '' time continue to induce deviations, become less and 



less capable of bringing about structural modifications 

 e — correspoDi during the life of the individual. Changes have now 

 3h Haeckel-ti ^q ^g perfected in a succession of individuals j and 

 LIS of vegetal ; ^-^us is the operation initiated of those subtle and 

 uisitions froiri: ^lore slowly modifying agencies which have been so 



^e place witt: 

 Heterogenesis 



Mr 



.ly 



pecies 



e ess 



have prop 

 ■ecurring 



Throughout this work, whilst I have been anxious 



10- ia to consider the various aspects of the subject with as 



are i much thoroughness as was necessary in order to be able 



ntiallyte fairly to attempt to establish the truth of the principal 



osd doctrines now advanced, I have also tried to simplify 



imal 



) 



Qf hot the problems as much as possible. A limitation was, 

 " ^1 ygirct moreover, necessitated by the pressing nature of those 



crrpxii ^*^^^ strictly professional duties, on account of which 



I was first induced to enter upon these investigations, 

 and in the midst of which the work has been carried 

 on. A rich harvest, therefore, remains for many other 

 workers who may wish to develop the subject in all its 

 collateral bearings. 



These volumes being, in great part, the record of a 



-each section of which 



I 



of this greats 

 t and sudden 

 . intermediate, 



lie gene''^^^'" 

 ntil Hon^^ 



r this vast 



series of current investigations- 



was written whilst the next division of the subject was 



