334 William E. Kellicott 



curves, is actually thrown forward into the latter part of "foetal" life 

 and is only apparently omitted. It is not now possible to consider the 

 rectal gland from this point of view because we have no positive knowl- 

 edge regarding its function, but the similarity between its curve of 

 growth and that of the brain is worth noting, though probably merely 

 accidental. 



Following this period of rapid and extensive adjustment comes that 

 of the most rapid growth which occurs during that time the animal 

 is dependent upon its own organs of direction and metabolism. During 

 the year of embryonic or "foetal" life it attains a weight of approxi- 

 mately 75 grams. During the first year of postnatal life, if our deter- 

 mination of time rate of growth is correct, it grows to a weight of about 

 300 grams — an increase of four times. During its second year, however, 

 the fish only little more than doubles its weight. It is, therefore, when 

 of from 75 to 300 grams weight that, as an independent organism, it is 

 growing the most rapidly (as measured by Minot's method) and that all 

 its independent nutritive processes must be relatively at their maximum, 

 and it is just at this time that the metabolizing organs are relatively 

 the largest. The spleen gives an excellent single example of this rela- 

 tion; in the fish this is the chief hsmatoplastic organ and during this 

 period of rapid growth the circulating tissues must be of prime impor- 

 tance, and correspondingly we find the spleen relatively very large. After 

 this early period of rapid growth increase in bulk is slower and the 

 relative size of the metabolizing organs decreases. But as already men- 

 tioned, late in life the brain and viscera cease their growth more rapidly 

 than the muscles and supporting tissues, which make up about 75 per 

 cent of the total weight. This relation is obviously non-adaptive, but 

 may, probably will, be found quite frequent if not typical among indeter- 

 minately growing forms. 



Donaldson, '95, has noted from the fragmentary observations of 

 Bischoff a similar relation in man and pointed out that there the 

 muscular system has grown more extensively than the brain and nutritive 

 system, suggesting that this was because the constructive processes become 

 less active in older individuals. His suggestion is well supported by these 

 more complete data from the dogfish, although here the problem is some- 

 what different because the muscles and connective tissues do not stop 

 growing at a definite time as in man and other mammals. 



We may now attempt to interpret briefly the peculiar growth rela- 

 tions of the liver and gonads. The liver seems to differ from the other 



