ASSORTIVE MATING IN CHROMODORIS ZEBRA 253 



only type of structural injury shown by specimens of this species 

 as obtained in the field amounted to a slight, and relatively in- 

 frequent, damage to the projecting margin of the mantle. This 

 statement was correct so far as concerns the several thousand 

 specimens which had passed through my hands in the preceding 

 two years. In 1917, however, collecting over the same territory 

 as in previous years and particularly in Fairyland Creek, a con- 

 siderable number of individuals were obtained in which a piece, 

 of varying size, had obviously been bitten from the middle of the 

 dorsal surface.^ As many as 20-50 per cent of the specimens col- 

 lected at one time would be found so injured. Animals thus 

 afflicted were seen to engage in normal copulation (with unin- 

 jured or with damaged partners, in equal frequency), and in the 



Fig. 3 Showing the type of injury found inflicted upon C. zebra in nature, 

 and its effect in producing puckering and a shortening of the "mantle length;" 

 a somewhat extreme case, dorsal view. The corresponding outline of an un- 

 damaged specimen is indicated approximately by dashes. 



great majority of instances they already showed signs of regen- 

 erative activity appropriate to the ultimate repair of the injury. 

 They were found to deposit good egg-masses. In all these cases 

 there was present a greater or less degree of puckering on the 

 dorsal surface (fig. 3), which caused the actual ''mantle length" 

 {B-C, figs. 1, 2) to be shorter than that of uninjured specimens of 

 about the same general size. This was especially true when the 

 wounded dorsal parts were stimulated by contact with the glass 

 plate during measurement. The amount of tissue lost as the re- 

 sult of injury was rarely considerable, and the total length {A-B, 

 figs. 1, 2) of the damaged nudibranchs seemed not to be seriously 

 influenced. Since it was desirable to include all the mating 



•• The nature, distribution, frequency, and significance of these injuries will 

 be discussed in another place. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY. VOL. 27, NO. 2 



