ASSORTIVE MATING IN CHROMODORIS ZEBRA 



259 



TABLE 2 



Correlation table for the mantle-length of 89 pairs of C. zebra. The larger member 

 of a pair is entered in the vertical columns, the smaller in the horizontal rows. 

 The class unit is 1 cm. The index of correlation is r = 0.518 ± O.OS^st. 



2. Other measurements. The degree of homogamy shown by 

 the measurements of other characters may be briefly considered. 



A. A series of mating pairs, comprising 89 normal uninjured 

 couples obtained successively in the field, whereof the mantle- 

 length was determined for each specimen, gave data summarized 

 in table 2. A small, homogeneous series was used, consisting 

 of a set of animals collected at one time and measured with par- 

 ticular reference to the mantle-length, rather than a larger 

 series selected from among the general field collections. Such a 

 selection would otherwise have been necessary, owing to the 

 relatively frequent occurrence, at this time, of injuries upon the 

 dorsal surface of Chromodoris. As previously stated, these in- 

 juries, in addition to making the nudibranchs difficult to meas- 

 ure, resulted in the distortion of the ''mantle length" through 

 puckering about the wound. 



The coefficient of correlation calculated from table 2 is 



r = 0.518 ± 0.0523 



The result is in sufficiently good agreement with that obtained 

 from the measurements of 'total length' (r = 0.608). The cor- 

 responding regression plot is given in figure 9. The number of 

 pairs (89) involved in the tabulation of mantle lengths is smaller 



