‘ Natural History of the United States. 215 
before the final adult stage is reached. Professor Agassiz, in his 
temarks on the succession of types, appears to argue that through- 
out clusses and orders in the Animal Kingdom there was a rising 
of grade among the species to the last; that is, among the species 
now existing as representatives of an order, the higher are of 
superior rank to those representing that order in any earlier time. 
But perhaps this point requires a farther survey of the facts. It 
0¢8 not seem to be established that the Carnivora of the present 
age are superior in grade to those of the Post-tertiary, or the 
Cephalopods of our own seas to those of the Reptilian Age. 
After considering many of the laws of relation among animals 
and between the animal and plant kingdoms, Professor Agassiz 
introduces an illustration of still wider unity embracing the 
paaical world at large, first suggested by his associate at Cam- 
bridge, Professor Peirce. As the facts have not been published. 
in this Journal, we cite a few paragraphs from the chapter. It 
is well known that the leaves of plants are arranged in spirals, 
Series 2, 4, 2, 3, vs) 2% 2, 21, etc.; in which the numerator an 
denominator of each term equals severally the sum of the nu- 
eat and of the denominators, of the two terms next pre- 
cedine : 
D e 
“Now, upon comparing this arrangement of the leaves in plants with 
ac : 
the law of phyllotaxis and the fourth column, finally, gives the normal 
Series of fractions expressing the law of phyllotaxis. 
Neptune, ——-60,129 62,000 
Uranus, 30,687 31,000 4 
Saturn, 10,759 10,333 4 
Jupiter, 4,333 4,133 z 
Asteroids, 1,200 to 2,000 1,550 3 
Mars, 687 596 ts 
Earth, 365 366 a's ; St 
Venus, 225 227 at 3 
Mercury, 88 87 az 
z ‘n this series the Earth forms a break; but this apparent irregularity 
admits of an easy explanation. The fractions 3, 3, $1 8) Ty 21 sar Cte, 
“xpressing the position of successive leaves upon an axis, by the 
