W. R. CARPENTER ON THE STRUCTURE OF ORBITOLITEB. 101 



forms to be still preserved. And thus we have in this group an 

 illustration of the principle, that if all genetic series were pre- 

 served, we should find no fixed boundary lines between species, but 

 that every form would be connected with other forms by grada- 

 tional transitions. 



Another lesson now comes in. I have always been one of those 

 who could not accept the doctrine of " natural selection" as a 

 vera causa. It is based on the idea of aimless or casual variations, 

 of which some prove more suited than others to become established 

 permanently. I never could feel that this gave any scientific ac- 

 count of the " origin of species," because it offered no explanation 

 of the causes of the variations by which the " fittest " came into 

 existence. Now here is a case in which we have at the present time 

 the entire series surviving, and this under the same conditions and 

 in the same dredging ; and since, to the eye of anyone but a skilled 

 Foraminiferalist, a specimen of the smaller type would not be dis- 

 tinguishable from a young specimen of the larger, I cannot think 

 that the creatures that prey upon them would know them apart. 



Fig. 12. 

 New disk of Orbitolite formed round fragment of previous disk. 



There is here, therefore, no room for " natural selection." To 

 my mind everything is indicative of development upon a deter- 

 minate plan, from the spiral to the excentric, then to the less ex- 

 centric, and then to the concentric form ; with a uniformly in- 

 creasing complication of the internal structure. 



