280 W. J. CROZIER 



It is true, however, that a number of instances have been 

 watched in detail where the animals after conjugation separated 

 in the absence of outside intervention, yet only one of them de- 

 posited eggs. In these instances the same two nudibranchs, 

 when placed together in a separate aquarium, were found to pair 

 together again within the next day or two, the result being that 

 the other specimen deposited an egg ribbon. 



These observations receive additional support from the field 

 collections. It is not uncommon to find two Chromodoris and 

 two nearby egg masses in the contents of a single dredge haul. 

 Moreover, in the one situation (described on a previous page) 

 where C. zebra has been found in 'pockets' under the cover of 

 stones, I was able to convince myself at different times that the 

 number of freshly attached egg ribbons noted in these places 

 corresponded to the number of animals present. 



Hence it is, I believe, safe to employ the idea that, broadly 

 speaking, reciprocal fertilization occiu-s in these nudibranchs; if 

 this is not true at each particular act of conjugation, at least 

 it can be held that animals of nearly the same size fertilize each 

 other, and that each animal deposits eggs. 



1. Number of larvae produced. The size of the egg mass de- 

 posited by C. zebra is a function of the size of the animal. This 

 concerns the length of the egg ribbon as well as its breadth, the 

 latter probably depending upon the diameter of the oviduct. 

 The number of eggs contained in each mass also depends upon 

 the size of the individual. The length of an egg ribbon and the 

 number of its contained eggs may, of course, be determined by 

 other, additional, influences — such, for example, as the number 

 of eggs already laid during the season. The reception of some 

 sperm is apparently sufficient to induce the beginning of egg lay- 

 ing, and there is a certain amount of evidence going to show that 

 once started the process of deposition continues automatically, 

 whether the ribbon of jelly contains fertihzed eggs or not. Thus, 

 if an individual be separated from its mate before insemination 

 has been carried to completion, it will in many cases lay a ribbon 

 of jelly which is of normal size, but in which only the part first 

 deposited contains fertilized eggs, these being sometimes fol- 



