REPORT ON THE CIENUS ORBITOLITES. 47 



Altogether, while I hold it utterly illogical to impute to "natural selection" a power 

 of originating any varietal forms whatever (since it can only take effect upon varieties 

 which have already come into existence), and find it difficult to conceive that it can have 

 had any share in even perpetuating the particular types of Orbitoline structure which 

 form the subject of this Report, the developmental advances by which they have been suc- 

 cessively evolved seem to me to lie altogether beyond the power of any known influence 

 of " environment " to account for. We have evidence, in the size and luxuriance of the 

 specimens of Orhitolites comj^lanata growing in the rock-pools of the reef, that a warm 

 temperature and abundance of food mny stimulate grotrth ; but we have no evidence 

 whatever that they can of themselves cause an advance in development ; and it seems 

 inconceivable that they should produce a complete change in the plan of a fabric. 

 There must have been an inherent capacity for elevation in certain of these organisms, for 

 any change in the " environment " to produce developmental advances ; for without such 

 capacity, no amount of warmth or food could do more than produce an increase of 

 groioth on the lower grade. And there must have been some fundamental difference 

 between that primordial jelly-speck which could evolve itself in a long series of 

 generations into the highest type of Orhitolites, and that which perpetuates the humble 

 form of Cornuspira still living under precisely the same conditions. Moreover, the 

 passage from the lower tyjae to the higher has always taken place (so far as we know) 

 through the same series of intermediate forms ; and each of these — as already pointed 

 out — continues to maintain its existence on its own grade. Finally, it would seem as if 

 the developmental capacity of the primordial germ exhausted itself in the production 

 of the most complex form of Orhitolites ; there being no reason whatever to believe that 

 it leads up to any higher form of organic structure. 



The general pointing of this study seems, therefore, to be, that the evolution of the 

 highly complex Orbitoline type from the simplest monothalamous jNlilioliiie, has taken 

 place according to a definite 2J^«", of which we have the evidence in the wonderful uni- 

 formity aud regularity of the entire sequence of developmental changes ; whilst we are 

 entirely unable to account for those changes, without attributing to the subjects of them 

 a capability of being affected hj external agencies in modes so peculiar as to indicate a 

 previous adaptation. The question whether the variations on which " natural selection " 

 takes effect are aimless, or whether they have a fixed direction, has so important a 

 teleological bearins;, that I have thought it worth while to work out with considerable 

 care an instance in which that fixity seems to me very conspicuous. And I would 

 specially point to the doubling of the radial stolons in the " duplex " tjrpe (pp. 27, 28) as 

 a change altogether meaningless in itself, but very significant when considered as anticipa- 

 tory of that greatest of all the developmental advances — the duplication of the annular 

 canals (p. 40) — whit-h marks the passage from the " simple" to the " complex" type. 



