;]28 William E. Kellicott 



gram, and the average ratio to total weight is 0.358 per cent. But from 

 birth onward the two sexes become entirelj^ distinct in both respects and 

 therefore must be described separately. 



Male. — In the male the weight of the gonads increases rapidly as 

 shown in Plate 7 to a maximum average of about 29 grams : the heaviest 

 testes weighed 31.8 grams. The total increase is nearly lOG times. 



The relative weight of the testes increases rapidly after birth from 

 0.358 to a first maximum of 0.775 per cent among males weighing about 

 400 grams. Then after falling to a ratio of 0.60 at about 900 grams 

 it recovers and rises rapidly to a ratio considerably higher than the first 

 maximum and then more gradually to a final maximum ratio of 1.15 

 (1.03 as averaged from the eight heaviest males). This ratio of 1.03 

 per cent is nearly three times that at birth and one-third higher than at 

 the first maximum. This is the only organ measured whose weight con- 

 tinues throughout the life to increase relatively to the total weight. 



Female. — From the time of birth the gonads of the females increase 

 at a somewhat slower rate than do those of the males. The rate is 

 only approximately uniform, so that the line given by plotting the weights 

 (Plate 7) is not a simple curve. The gonad weights of the larger 

 females are not strictly comparable with each other because, at the 

 season when they were weighed (July and August), some of the ovaries 

 still contained one or more large yolk-filled ova, while from others the 

 mature ova had been completely discharged so that the weight of the 

 ovary was considerably altered. In Plate 7 the ovaries that contained 

 large ova are enclosed in small circles. Only one female of less than 

 3600 grams (the exception weighed 2266 grams) was found with large 

 eggs in the ovary. Similarly only one of less than 3250 grams (the ex- 

 ception weighed 1998 grams) contained developing embryos in the ovi- 

 ducts, while all of the 26 specimens observed above this weight contained 

 embryos. The females of this dogfish therefore do not become mature 

 until they have reached a weight of at least 2000 and usually 3000 grams; 

 the length of such fish is roughly 90 and 100 cm., respectively, and their 

 age probably four or five years. 



The relative weight of the ovary rises like that of the testes to a 

 primary maximum in fish of about 400 grams. This maximum is 

 not so high as in the male, being only 0.675 per cent. This is followed 

 by a fall to a ratio of 0.43 in fish of about 1700 grams. After remain- 

 ing at about this point for some time the ratio tends to rise a second 

 time as in the male, though not to the same extent. Probablv this 



