Causes of Variation. 95 



tlie chfimber-systcms, while among the Sponges the variation 

 is in tlie microscopic detail. " One may speak of the micro- 

 scopic form of Foraminifera, but not of microscopic elements." 



The complexity of the shell is merely in the multiplicity of 

 chambers and the manner of their intercommunication. The 

 process of growth, even in the complex 0. complanata, is in 

 all respects identical with that in other species, and in no 

 essential feature differs from that of PeneropUs. What Dr. 

 Carpenter designates as a " higher specialized type of struc- 

 ture " does not represent an advanced degree of specialization 

 in any part ; nor can we discover any advantage to the organ- 

 ism arising therefrom. It is true there is an advance in com- 

 plexity ; but unless accompanying this there is an evolution 

 in function, or unless it results from some effort of adaptation 

 which confers some benefit upon the organism, it seems not 

 proper to regard complexity of shell-structure as a proof of 

 biological advancement. 



Seeking for an explanation of the cause of the increased 

 complexity of shell-structure, so beautifully illustrated in the 

 Milioline family, the writer was led to the conclusion that it is 

 entirely due to the favourable conditions of life and the abun- 

 dance of food available. It is true, as already said, this may 

 be regarded as a mere statement of the influence of environ- 

 ment causing variation ; but a careful consideration of the 

 subject will show that there is a broad distinction between 

 environment as a cause of variation and adaptation to environ- 

 ment ; for in this case we are unable to perceive any benefit 

 to the organisms arising from their adaptation to changed 

 conditions. 



If it be said we can seldom discover the benefits supposed 

 to be derived from adaptation, it may be answered that it is 

 usually possible to infer how the changes observed may prove 

 beneficial. In the case under consideration, however, an 

 examination of the changes that have taken place does not 

 indicate any possible benefit to the organism. The multipli- 

 cation of chamberlets necessitates very intimate intercommu- 

 nication for the transference of food and the continuation of 

 the processes of life. The organism is not thereby better 

 adapted to its surroundings, but is made more dependent 

 for its existence upon the continuance of the favourable 

 conditions under which it has developed. The advance in 

 complexity — the multiplication of chamberlets — would only 

 be possible under the most favourable conditions, for all the 

 nutriment received by the interior segments must be col- 

 lected by the sarcode at the margin of the shell, and the 

 necessary food could only be obtained where the supply was 



8* 



