FECUNDITY OF THE PACIFIC SARDINE 



429 



provided a clieck on the aeciiracy of tlie ovum 

 counts and yielded a larger sample tlian could 

 liave been easily examined on one slide. 



Eacli sample of ova was projected in the scale 

 l)rojeclor at a magnification of 50X. Tiie pro- 

 jected ovum diameters were measured to the 

 nearest millimeter. "Wiicn doubled, this measure- 

 ment gives the actual ovum diameter in hun- 

 dredths of a millimeter by 0.02 mm. units. 



If the sample of ova contained no distinct (by 

 size) group of developing ova, the diameters of the 

 larger ova in the sample were measured. The 

 largest ovum diameter was used as a measure of 

 the ovarian development for these early stages 

 when no modal or other central value could be 

 obtained. Figure 1-a and b and figure 2-a and b 

 show ovum diameter frequencies from ovaries in 

 these stages of development. The dotted lines in 



figures 1 and 2 represent 95 percent confidence 

 limits of the counts. 



If the ovary was advanced enough so that a 

 distinct group of yolked ova had differentiated by 

 size from the smaller yoli\ed ova, enough ova 

 (generally 100 to 200) 0.22 mm. or larger (i. e., 

 containing yolk) were measured to delimit clearly 

 this most advanced group of developing ova. 

 When the size range of this group was determined, 

 all ova in that size range on the slide were counted. 

 Figure 2-c, d, e, f, g, and h shows ovum diameter 

 frequencies from ovaries in these stages of develop- 

 ment.' The most advanced groups of ova shown 

 in these figures consist of opaque ova except the 

 group shown in figure 2-h which consists of trans- 

 lucent ova. Xo perivitelline space has formed in 



' The mullimodal distribution of diameters of developing intraovariun ova 

 of the Pacific sardine was first demonstrated and figured by Clark (1934). 



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Fig. 2-G 

 STAGE "b" 



Estimated number of ova 

 .02- 20mm 510,000 

 .22-. 36mm 20,000 



Fij 2-b 

 STAGE "C" 



Estimoted number of ova 

 02- 20mm 640,000 

 .22-.40mm 43,600 



Fig 2-c 

 STAGE "E" 



Estimaled number of ova 

 22- 40mm 52,000 

 42- 52mm 29,500 



Fig 2-d 

 STAGE "E" 



Estimated number of ova 

 22-44mm 69,100 

 46-. 60mm 35,300 



Fig 2-e 

 STAGE "F" 



Estimated number of ovo 

 .22- 46mm 39,600 



.48- 70mm 29,100 



22 26 30 34 38 42 46 50 54 58 .62 66 70 



OVUM DIAMETER IN MILLIMETERS 



Figure 2-a, b, c, d, e. — Sardiiu' iiitra-ovariaii ovum diamotor frequeiicie.-; (.-ice p. 4'iO). 



