ASSORTIVE MATING IN CHROMODORIS ZEBRA 



251 



length of the nudibranchs was 11-12 cms., with a range of 4-18 

 cms., these measurements were of sufficient refinement for sta- 

 tistical purposes. The measurements were always made in 

 duplicate. , 



Fig. 1 Chromodoris zebra, seen from the right side and above, showing 

 dimensions measured. A~B, total length; C-B, mantle length; D-E, distance of 

 genital papilla from the mouth. The animal is shown as it appears when creep- 

 ing upon a horizontal surface. 



Fig. 2 Chromodoris zebra. The animal is shown as it appears when placed 

 dorsal surface downward upon a glass plate which is moistened with seawater. 

 The characteristic reaction in which the lateral margins of the foot are closely 

 approximated when the organ is not applied to a flat surface should be noted. 

 Lettering as in Fig. 1. (See text.) 



The dimensions considered will be understood by reference to 

 figures 1 and 2. They include: 



1) the total length, from the anterior edge of the buccal veil 

 to the posterior termination of the foot; 



2) the mantle length, from the anterior margin of the buccal 

 veil to the posterior edge of the caudal veil; 



