82 
Then the septa alter in this respect and finally in extreme parage- 
rontic substage the approach of extinction is heralded by the close 
approximation of several septa, as has already been stated above. 
The greater number of these that show this change indicate that the 
species possess great vital power and has a prolonged old age 
changing slowly, and the small number show that senility is a more 
rapid process. In the higher, more specialized Nautiloids and 
Ammonoids there are usually only two or three approximate septa 
in old age; in Endoceras, a radical type, there may be as many as 
twenty-two which show degeneration in the rate of growth. There 
are other phenomena of a similar character which might be noticed 
in this connection, but must be deferred to future publications. 
Naturalists have as a rule understood the differences between the 
organic molecular increase that takes place within cells which is the 
simplest form of growth, and that which follows this and builds up 
the tissues of the body by the division of cells. Both of these pro- 
cesses, although distinct from each other, result in additions to the 
bulk of the whole body of the organism and come properly under 
the head of growth. But while both are thus constructive so far as 
the body is concerned, only one can be considered constructive or 
anabolic while the other is essentially destructive or catabolic so far 
as the cell itself is concerned. 
The function of nutrition and the nature of the organic structure 
are the two essential factors of growth, and this term, z. ¢., growth, 
also obviously applies to the morphology of metabolism, consisting of 
intracellular increase, or anabolism, and cellular development, or 
catabolism, and the phenomena resulting from the alternating 
action of these in ontogeny. This at once shows that growth is not 
simply progressive addition to the bulk of the body, since the mul- 
tiplication of cells by fission is in itself catabolic or developmental 
so far as the cells are concerned. Further than this the ultimate 
results of catabolism are of the nature of reductions as is shown by 
Minot’s law,* and also by Maupas’ observation + on the old age of 
the agamic cycle in Infusoria and the results of late researches on 
amitosis in cellular fission. ‘These and the actual reduction of the 
body taking place in extreme senility show that the term growth 
* “* Senescence and Rejuvenation,’’ Journ. Phys., xii, No. 2, 1891, and address on “‘ Cert. 
Phen, of Growing Old,’’ Am. Assoc. Adv. of Sc.i, xxxix, Aug., 1890. 
t ‘‘ Recherches expérimentale sur la multiplication des Infusores ciliés,’’ Arch. de Zool. 
experim. et gén., Sr. 2, vi, pp. 165-277, et ibid., vii, pp. 149-517. 
