278 



W. J. CROZIER 



Expt. 10.57. April 24. In an aquarium containing 18 freshly col- 

 lected chromodorids, a specimen 13.5 cms. long was seen to be unsuc- 

 cessful in attempting to copulate with another 8.7 cms. in length; 

 15 min. later it 'refused' a second one, 9.5 cms. long. After 30 min. 

 it mated successfully with an individual which measured 12.2 cms. 



Expts. 10.61-10.64. In each of the following cases the animals 

 whose lengths are tabulated together were placed in a single aquarium. 

 The individuals which conjugated are enclosed in brackets. 



Lengths. 



14.0 

 13.0 

 12.5 

 12.6 

 10.3 



These individuals were all collected on May 18, but in different 

 places, (a) and (c) being obtained in Millbrook Creek, the rest in 

 Fairyland Creek. They were 'ear-marked,' so as to be separately 

 recognizable, by having a small piece clipped from different parts of 

 the mantle; this injury caused the nudibranchs no inconvenience. 



After two hours, a was observed unsuccessfully attempting to copu- 

 late with e, and b with c. On May 19, there were found pairing to- 

 gether a with b and c with d. The animals were isolated, and b and d 

 subsequently laid egg masses. 



VII ON THE CONSEQUENCE OF HOMOGAMY 



This paper is concerned primarily with the demonstration of 

 the fact of assortive-mating in Chromodoris. It may never- 

 theless be well to consider some of the possible results of homog- 

 amy in this nudibranch, although several of the matters con- 



