1908] Eofoid. — Exuviation and Autotomy in Oeratium. 361 



1. Its general occurrence. — Few collections from oceanic wat- 

 ers off San Diego in which Ceratium is found fail to contain some 

 instances of autotomy. It appears, moreover, in practically all 

 of the long-horned species belonging to the C. tripos and C. ma- 

 croceros groups as well as in the more aberrant forms such as G. 



Figs. 13-15. — Ventral views of Ceratium gallicum showing proportionate 

 reduction of the horns in autotomy. X 220. 



reticulatum and C. clavipes. The examination of a considerable 

 range of collections at San Diego has afforded me evidence that 

 this mutilation is more common in certain species, notably in C. 

 biceps, C. gallicum (figs. 13-15) and C. trichoceros (figs. 16-19), 



