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W. J. CROZIER 



tageous, as a large number of couples were in this way obtain- 

 able at the same time. It is also important as pointing to the 

 possible existence of specific secretions which may induce pairing. 

 Twenty-four to forty-eight hours after the nudibranchs had 

 been put into an aquarium, the mating-pairs noted were re- 

 moved, placed separately in small dishes, and as soon as pos- 

 sible submitted to measurement. In this way data were secured 



Fig. 15 Regression plot {r, r) for data in Table V; r', r', regression line ob- 

 tained from pairs collected in nature (Fig. 8). 



regarding the lengths of the constituents of 119 pairs (cf. fig. 7). 

 These figures are arranged in table 5, and in a regression plot 

 (fig. 15). The index of correlation for the total lengths of the 

 components of mating couples is here r = 0.721 ± 0.023. 



2. Comparison with normal conditions. The degree of homo- 

 gamy exhibited in this series of laboratory matings is appreciably 

 higher than that found for the pairs collected in the field (fig. 

 15). This may be the outcome of chance variation incident to 



