Growtli of Brain and Viscera in DoiiTi^li 329 



tendency to rise a second time here is periodic and seasonal. For if 

 we consider the distribution of only the ovaries containing large ova 

 we see a considerable rise in relative weight, but the weights of the ovaries 

 from which all mature ova have been discharged do not give an increasing 

 ratio but one that is practically uniform. Probably therefore this gen- 

 eral curve of relative weights is a composite and should be resolved 

 into two components as in Plate 7, Curves A and B. 



Discussion of the Data 



Before attempting to interpret these data or to compare them with 

 other more or less similar data from other forms we may compare the 

 data concerning the various organs among themselves. 



Of course these curves do not contain a known time factor and this 

 must be borne in mind during their consideration and in comparing 

 them with other data. The measurement of a large number of dog- 

 fish taken at random might give us some information regarding the 

 average time rate of growth for the first few years of life, but so far 

 as I know we have no such data. Of the specimens which I examined 

 the first eighty were collected at random, since they included practically 

 all of the fish taken in almost daily hauls of the trap for six weeks. 

 Upon plotting these fish according to weight and length we get curves 

 w^ith several maxima in their early parts, indicating the total weight and 

 length with age as follows : 



Age 



Birth 



1 Yr 



2 Yr 



3 Yr 



There is considerable overlapping, and after the fifth year the indi- 

 viduals are so scattered that they form a more or less continuous and 

 irregular line. The distribution commences to become uneven after what 

 is apparently the second year. It can not be told with much probability 

 whether or not the sexes grow at the same rate, though it seems likely 

 that the males at first grow faster than the females, but after the third 



