1908] Kofoid. — Notes on Species of Ceratium. 391 



as yet expanded to the size that they later attain in the older 

 stage. 



As above stated, C. lamellicorne is smaller than G. platycorne. 

 This applies to the length of the horns, which, as I have shown in 

 the preceding paper, might be expected to undergo changes in 

 length during the life of the individual by processes of autotomy, 

 regeneration, or growth of regenerative type. Lateral expansion 

 of the median margin of the antapical horns is also theoretically 

 possible. The midbody, however, is typically larger in C. platy- 

 corne than in 0. lamellicorne. I have no evidence that the mid- 

 body of Ceratinm is subject to an increase in size comparable 

 with that which may occur in the horns. 



A consideration of the conditions pertaining to the skeleton 

 during schizogony, especially the fact of compensatory regener- 

 ation of the new skeletal moiety, and the essential uniformity of 

 individuals in chain, would seem to preclude the existence of any 

 such young and old stages of the individual with accompanying 

 differences in dimensions due to gro\\'th, such as would neces- 

 sarily follow from Karsten's point of view with regard to these 

 two forms. I find no such prevalence of intergrades as the idea 

 that C. platycorne is the old stage of C. lamellicorne would lead 

 us to expect. An examination of a large number of sketches of 

 these two species of Ceratium. from the oceanic plankton off San 

 Diego leads me to believe them to be distinct species with a con- 

 stant size difference and not age forms of one. 



Karsten's ( :05) name dilatata is preoccupied by Gourret's 

 ('83) C. dilatatum. Gourret seems also not to have known of 

 Ehrenberg's ('74) description of C. candelabrxim and among 

 other names which he has applied to various forms of that poly- 

 morphic species, he uses C. dilatatum. Because of Gourret's 

 prior use of this name I here propose for this smaller species the 

 new name of C. lam,ellicorne. 



Zoological Laboratory, University of California, 

 April 2, 1908. 



