EARLY DEVELOPMENT OF THE TEN-POUNDER 



635 



period. The variation in the body parts during 

 the mid-metamorphic period and the difficulty in 

 separating the shrinking larvae from those in- 

 creasing in length preclude fitting regression lines 

 for this period. 



Regression lines for the late metamorphic and 

 juvenile periods were determined from specimens 

 138 mm. or less in standard length as my data be- 

 yond 138 mm. are insufficient for calculating 

 regressions. I have extended the calculated re- 

 gression lines beyond 138 mm. as broken lines to 

 determine whether the relation suggested by 

 smaller specimens continues beyond 138 mm. The 

 insets in the graphs expand the scale for specimens 

 less than 50 mm. to better show the relationship 

 in this size range. 



Head length. — During the leptocephalus period 

 the. head length increases 0.055 mm. for each milli- 

 meter increase in standard length (fig. 25, table 

 11). During the early metamorphic period the 

 increase is 0.005 mm. for each millimeter decrease 

 in standard length. During the late metamorphic 



Figure 23. — Caudal osetology of a 30.9-rnni. early meta- 

 morphic larva (fig. 9). Density of stippling indicates 

 intensity of alizarine red stain. 



Original, individual measurements (table 10) 

 plotted on the graphs showing relations of various 

 body parts to standard length (figs. 25 to 30) were 

 used in the calculation of the regression lines 

 (determined by the method of least squares). 

 Table 11 presents the statistics describing the re- 

 gressions of the body parts on standard length. 

 Arithmetical plots of individual variates indicated 

 that in most instances the formula for a rectilinear 

 regression, Y=a+bX, adequately describes the 

 relationships. 



Three regression lines were calculated for the 

 relations of head length, eye diameter, body depth 

 at pectoral, snout to insertion of the dorsal fin, and 

 snout to insertion of the anal fin to standard 

 length ; one for the leptocephalus period, one for 

 the early metamorphic period, and one for the late 

 metamorphic and juvenile periods combined. A 

 single line was calculated for the regression of 

 snout to insertion of the pelvic fin on standard 

 length (late metamorphic period into juvenile) 

 since this fin did not develop until the early meta- 

 morphic period and I had few values for this 



Figure 24. — Caudal osteology of 25.9-mm. late meta- 

 morphic larva (fig. 13). Stippling indicates alizarine 

 red stain. 



