GROWTH OF IDEAS 267 



these according to our skill ; but there is a sub- 

 jective limit to this skill in all of us. 



The first edition of the History of Creation 

 Haeckel's first attempt at popularising had a good 

 deal of inequality in this respect. To begin with, 

 the book had the air of an extempore deliverance. 

 Its success was very largely due to its being cast in 

 this form. But there was a good deal that could 

 be improved here and there, and was improved in 

 the later editions of the work. In the tenth 

 edition, as we now have it, it is a splendid work in 

 regard to the illustrations, for instance. But the 

 first edition was merely provided with a few very 

 crude woodcuts in outline. Some of them were 

 very clumsy. In comparing different embryological 

 objects the same blocks were used sometimes, 

 and this would give rise to misunderstanding in 

 the mind of the reader. For instance, there was 

 question of demonstrating that certain objects, 

 such as the human ovum and the ovum of some 

 of the related higher mammals, were just the same 

 in their external outlines. This fact is quite correct 

 and established to-day. If I draw the outline, and 

 write underneath it that as a type it is applicable 

 to all known ova of the higher mammals, including 

 man, there is no possibility of misunderstanding. 

 But if I print the same illustration three times 

 with the suggestion that they are three different 

 mammal-ova, the general reader is easily apt to 

 think, not only that they are identical in the 

 general scheme of this outline, but also in internal 

 structure. He imagines that the ova of man and 



