1908] Kofoid.- — Exuviation and Autotomxj in Ceratium. 369 



An examination of the details of this table brings out certain 

 significant tendencies. These appear perhaps most clearly in C. 

 gaUicum. A presumably normal individual has the apical, right 

 and left antapicals in the ratios of 4.8 — 3.8 — 4.5, in a second 

 case 7.2 — 4.5 — 5.0. In the six cases of autotomy recorded the 

 apical retains an excess in length in all but two instances and in 

 both of these there was evidence of recent schizogony and active 

 growth of the newly formed apical. It is also noticeable that in 

 four cases a considerable shortening of the apical is attended by 

 much foreshortened antapicals. In the two normal individuals 

 included in the table the relative lengths of the right and left 

 antapical are 1 to 1.2 and 1 to 1.1 respectively. The average for 

 all records of this species in the tables is 1 to 1.25 and for the six 

 which have undergone autotomy 1 to 1.27 (range .85 to 1.7). In 

 all but one instance after autotomy or regeneration or both, the 

 individuals of C. gallicum recorded in this table show the left 

 horn slightly longer than the right. These processes are thus 

 regulatory and tend to preserve the norm of the species. 



An examination of the data of C. inflexum yields somewhat 

 similar conclusions. There are three instances (5, 6 and 10 of 

 the list) in which the apical is noticeably disproportionate. One 

 at least of these (10) is due to recent schizogony. In the other 

 nine cases there is a tendency for a short apical to accompany 

 short antapicals. In all but two instances (2 and 9) the left 

 horn exceeds or equals the right in length, as in C. gallicum, 

 and in about the same ratios, averaging 1.26 (or omitting the 

 aberrant 6 the average becomes 1.15). The normal relation 

 of longer left and shorter right horn thus prevails in all but two 

 cases of the twelve. One of the two instances (12) of dispro- 

 portionately long right horn presents significantly no less than 

 three incipient section planes forming in the longer right horn 

 at about 1.7 transdiameters from the midbody. The completion 

 of this incipient autotomy w^ould bring the ratio of the antapicals 

 to 1.3, nearly the norm for the species. The other case (6) of 

 disproportionate length of antapicals shows not the least trace of 

 approaching regulatory autotomy. In both of these the defi- 

 ciency of the left horn is slight. The ratio of the two horns 

 after autotomy is in general thus approximately the same as that 



