Grade 1. '.'.hlte but stilx Jslender, blood vessels on the surface not developed, 



firm to the touch. 

 Grade 2, Thicker than 1, blood vessels developed on the surface, but milt does 



not yet flow out when the spermatic canals are pressed (Figure 2, 



upper right) . 

 Grade 3. Thicker, blood vessels fiarther developed, milt flows out vrtien spenratic 



ducts are pressed (Figures 1 and 2, upper left). 

 See figures 1 and 2. Examples of gonads of each grade are pireaerved in 

 formalin at the Palao Tropical Biological Station. 



[TN: Figure 1 has the following captions..^ 



Figure 1 Showing the lack of correlation between size of gonads and the degree 



of maturity. 



Upper right - Testis from a fish weighing 3a06 kg. Gonad is 17.5 cm long and 



weighs 55 g. 

 Upper left - Ovary firom a specimen weigning 3.iV5 kg. The gonad is 16.5 cm 



long and weighs 80 g, 

 Lov'er left - Testis from a specimen weighing 5o66 kg. Length 22 cm, weight 



185 go 

 Lower right - Ovary from a specimen weighing 5,(>U kg. Length Z^ cm, weight 



2^5 g. 

 [Captions on Figure 2 J 



Figure 2 Some of the grades of maturity of gonads 



Upper right - Testis from a specimen weighing 5.81 kgc Length 2^.5 cm, weight 



150 g. Grade 2, 

 Lower right - Ovary from a specimen weighing 5«32 kg. Length 22 cm, weight 



135 g. Grade 2. 

 Upper left - Testis from a specimen weighing 7.62 kg. Length 25 cm, weight 



290 g. Grade 3. 

 Lower left ~ Ovary from a specimen weighing 7.38 kg. Length 23.5 cm, weight 



175 go Grade 3. 



Fish from H schools were examined, the total number of specimens being 135 « 

 The weight range was from 1.8 kg to 8 kg. In all of the specimens examined the 

 gonads were advanced in maturity to some degree, and they were all large enough so 

 that the ovaries and testes could be readily distinguished by their outward appear- 

 ance. 'With regard to this point the author is reminded that year before last in 

 February and in May he examined at Shimoda in Shizuoka Prefecture the gonads of a 

 number of skipjack in thd same size range as those taken at Palao, that is from 2 

 to 7 kg In weight, and he found that in the skipjack landed at Shimoda the gonads 

 were slender and were attached to the dorsal wall of the body cavity. They were 

 not markedly developed and it vi&a impossible to tell the ovaries and testes apart 

 by their outward appearance. The gonads of the yellowfin tuna which at Palao are 

 taksn mixed in with skipjack, and which are the same size as the skipjack of the 

 schools with which they are associated, are developed only to the degree found in 

 the gonads of the skipjack taken at Shimoda. On the other hand the large specimens 

 of yellowfin taken on the longlines of the Fisheries Experiment Station's tuna in- 

 vestigation boat have fairly mature gonads which show the same stage of development 

 as the gonads of the skipjack taken in Palao waters. Thus a good basis for compari- 

 son is provided on this point. 



The weights of the gonads ranged from 20 to 330 grams, an extremely wide range. 

 Within the area covered by this investigation the weight of the gonads was a function 



