2O4 CARL L. HUBBS. 



Several possible sources of error in the use of this formula are 

 apparent. The scales do not develop until considerable growth has 

 occurred. As the length of the scale is usually measured, for the 

 purposes of growth computations, only from the focus cephalad 

 to the basal margin, an unequal growth of the different fields of 

 the scales mav introduce an error. There is some variation in 



j 



the time of formation of the annuli. The scales often overlap 

 less widely in young fishes than in adults, rendering the computa- 

 tion of size for the first winter too small. Again, the length of 

 the fish is measured, for growth computations, from the tip of the 

 snout to the base of the caudal fin. There is thus included the 

 length of the head, which becomes relatively shorter with in- 

 creased size in most fishes. As the formula assumes that the 

 head and body increase in the same ratio, the computed length for 

 the young fish at a given stage would be accurate only if the head 

 were then of the same proportional length. The head being rela- 

 tively longer, however, the computation is too small. It is doubt- 

 less these factors (probably all of them) which have rendered the 

 computed length of the young of Amphigonoptcrns at the time 

 of the formation of the natal annulus (just after birth) to be 

 less than the observed length at that stage (20 to 32 mm., instead 

 of 29.0 to 35.5 mm.). 



TABLE VII. 



COMPUTED RATE OF GROWTH OF FEMALES OF AMPHIGONOPTERUS AURORA.! 



Period of Growth. Growth. Specimens 



To formation of natal annulus 2032 mm. 70 



Thence to end of first winter 29-68 mm. 69 



Between first and second winters 14-35 mm. 20 



Between second and third winters 12-27 mm. 20 



Between third and fourth winters 1318 mm. 5 



Between fourth and fifth winters 13 mm. i 



Between fifth and sixth winters 4 mm. i 



1 Based upon material collected near Piedras Blancas during the first week 

 of June, 1916. 



It is evident from these figures, as well as from supplementary 

 data obtained from collections made on other occasions, that the 

 growth of the first half year (between birth and the first winter) 

 is greater than that of any subsequent whole year. This estimate 



