XL] THE GENEALOGY OF ANIMALS. 277 



to be sought in the external world ; but if we carry our 

 inquiries as far back as this, the distinction between 

 internal and external impulses vanishes. On the other 

 hand, if we confine ourselves to the consideration of a 

 single organism, I think it must be admitted that the 

 existence of an internal metamorphic tendency must be 

 as distinctly recognized as that of an internal conservative 

 tendency ; and that the influence of conditions is mainly, 

 if not wholly, the result of the extent to which they 

 favour the one, or the other, of these tendencies. 



III. There is only one point upon which I funda- 

 mentally and entirely disagree with Professor Haeckel, 

 but that is the very important one of his conception of 

 geological time, and of the meaning of the stratified 

 rocks as records and indications of that time. Con- 

 ceiving that the stratified rocks of an epoch indicate a 

 period of depression, and that the intervals between 

 the epochs correspond with periods of elevation of which 

 we have no record, he intercalates between the different 

 epochs, or periods, intervals which he terms "Ante- 

 periods/' Thus, instead of considering the Triassic, 

 Jurassic, Cretaceous, and Eocene periods, as continuously 

 successive, he interposes a period before each, as an 

 "Antetrias-zeit," " Antejura-zeit," "Antecreta-zeit," "Ant- 

 eocen-zeit," &c. And he conceives that the abrupt 

 changes between the Faunae of the different formations 

 are due to the lapse of time, of which we have no 

 organic record, during their " Ante-periods." 



The frequent occurrence of strata containing assem- 

 blages of organic forms which are intermediate between 

 those of adjacent formations, is, to my mind, fatal to 

 this view. In the well-known St. Cassian beds, for 

 example, Palaeozoic and Mesozoic forms are commingled, 

 and, between the Cretaceous and the Eocene formations, 

 there are similar transitional beds. On the other hand, 



