DESIGN IN THE ORGANIC WORLD. 445 



specialized type came into existence, in which that most won 

 derful feature of its organization, the feather, arose out of the 

 scaly covering of its Reptilian ancestors, in which its heart came 

 to be divided into four chambers instead of three, and the arrange 

 ment of its blood-vessels altered accordingly, in the establishment 

 of the &quot;complete double circulation,&quot; that insures the perfect 

 aeration of the blood needed for the maintenance of the extra 

 ordinary muscular energy by which the feathered wings can 

 sustain the body in flight, I cannot see that &quot; natural selection &quot; 

 throws the least light There is, as I have already pointed out, 

 an adaptation in the several parts of the structure of the Bird, 

 not only to one general result, but to a consentaneous action in 

 bringing about that result, which shows itself to be more complete, 

 the more closely it is scrutinized. And on the hypothesis of 

 &quot;natural selection&quot; among &quot;aimless&quot; variations, I think it could 

 be shown that the probability is infinitely small, that the pro 

 gressive modifications required in the structure of each individual 

 organ to convert a Reptile into a Bird, could have taken place 

 without disturbing the required harmony in their combined 

 action ; nothing but intentional pre-arrangement being competent 

 to bring about such a result. And the point on which I now* 

 wish to fix your attention, is the evidence of such pre-arrange 

 ment that is furnished by the orderly sequence oj variations alloiuing 

 definite lines ot advance. 



I shall illustrate this, in the first place, by a general outline 

 of a Memoir which I last year presented to the Royal Society, in 

 which I embodied the final results (as relating to this subject) of 

 an inquiry on which I had been engaged for forty years into the 

 organization of the Foraminifera ; a group of marine animals of 

 tlie simplest protoplasmic nature, which yet form for themselves 

 shelly coverings of singular regularity and complexity of structure, 

 the aggregation of whose remains forms many important Lime 

 stone strata (as the Nummulitic limestone of which the Pyramids 

 are built, and the Miliolite limestone which has furnished the 

 chief building material of Paris), whilst Chalk is a product of their 

 disintegration. My studies of this group began with a compara 

 tively gigantic type called the Orbitolite ; which is a shelly disk, 

 sometimes attaining the diameter of an inch, living at the present 



