COXFOR^nTY OF STRUCTURE. 107 



to have a " free-and-easy " time. I am a sort of sloio and easy- 

 man, but there is one difficulty in my mind, which prevents 

 my acceptance of Darwin's theory of the origin of man. If 

 like begets like, how did the monkey beget a man ? And if like 

 begets like, why not man beget a monkey ? But the particular 

 difficulty in my mind is this, — how the monkey, when he jumped 

 from moukeyhood to manhood, left that long tail behind. 



Prof. Agassiz. I will answer part of your question. The 

 kind of monkey from which Darwin supposes that mankind is 

 derived, had no tail at all. The gentleman has started one 

 of the most interesting questions. The conformity of struct- 

 ure throughout the animal kingdom, is one of the most start- 

 ling features in creation, and that conformity is so great that 

 the ablest naturalists everywhere have demonstrated the fact 

 by innumerable comparisons. At first, it would seem that in 

 this configuration there are several striking differences, so far 

 as form and general appearances are concerned ; but when you 

 begin to compare those individual parts in the changes they 

 undergo with growth, you are led to recognize such a unity of 

 organization, that the question may be, on the other side, 

 what is the significance of the difference ? And it is just that 

 play on the opposite sides of the question, when it presents it- 

 self to our minds, which causes our progress in knowledge, and 

 at the same time leads to those wide and marked differences 

 in our estimation of things. Now, in the earlier condition of 

 life, when the vertebral column is just forming, there are in- 

 dependent vertebrse sticking out from the outline of flesh in 

 the human species, as well as in monkeys and all other ani- 

 mals, so that the embryo of the monkey, up to a certain 

 period, and the human embryo of a corresponding period, 

 will exhibit a condition of the extremity of the vertebral 

 column as a caudal appendage, of exactly the same appear- 

 ance, and exactly the same form. Why is it that in one 

 these vertebra become consolidated with one another, and 

 remain as Os Coccygis at the lower end of the Os sacrum, and 

 in monkeys increase in number, become movable, and form 

 a real tail, we do not know ; but the fact exists, that in 

 some one condition of their growth, the two agree perfectly. 

 The great problem is to account for the fact, that while there 

 is this uniformity and blending, there are at the same time 



