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Puget Sound Marine Sta. Pub. 



Vol. 1, No. 11 



weights it was determined that the unabsorbed portion of the yolks of the 

 12 fish from the dark was 17.72 per cent heavier than that of the 12 

 from the light; at the same time the 12 fish from the dark without their 

 yolk-sacs weighed 5.310 grams, and the 12 from the light without their 

 yolk-sacs weighed 5.030 grams, a difference of 5.57 per cent in favor of 

 the fish from the dark over those from the light. Thus, although there is 

 much less yolk absorbed by the fish in the dark, there is yet a greater 

 weight of organized tissues. 



Weight comparisons were again made January 18. About 50 fish 

 were taken by a single sweep of the strainer from each trough and 40 

 were picked at random from each of these groups. The fish were first 

 dried on a linen towel and then on filter paper. The 40 taken from the 

 dark trough weighed 19.03 grams, and the 40 from the light trough 17.30 

 grams. According to these weights the 40 from the dark trough weighed 

 10 per cent more than the same number from the light. 



The following day a dozen fish were taken from each trough at ran- 

 dom and measurements taken similar to those made January 9. Table 3 

 records the maximum and minimum dimensions between which they varied, 

 with the average for each group. Of those taken from the 



Table 3. The dimensions of fish from each trough compared 



Differences in averages 



dark two fish had their ventral slits closed, in the remainder 

 the slits varied in length between 6 and 9 mm., and in width be- 

 tween .6 and 2 mm., the average dimensions of the openings including the 

 two fish with the closed slits being 6.1 mm., in length and .8 in width. 

 Of those taken from the light eight had the ventral slit entirely closed 

 and in the remaining four it was all but closed. These figures confirm the 

 statement previously made, that a much greater yolk absorption took place 

 in the fish kept in the light. 



The last determination of comparative weights before feeding began 

 was made January 29. Forty fish taken at random from each trough gave 

 the following results: those from the dark trough weighed 21.39 grams 

 and those from the light trough 19.22. These weights show that the fish 



