1908] Kofoid. — Exuviation and Autotomy in Ceratium. 367 



But 5 of the 21 species, to wit : candelabriini, heterocampttini, 

 macroceros, seta and vultitr were represented only by normal in- 

 dividuals. This is of little significance except in the cases of 

 C. hucephalum, C. cavdclahrum, C. lieterocamptum and C. seta 

 in which, according- to my observations elsewhere, autotomy is 

 relatively rare. It occurs very generally in C. macroceros and C. 

 vidtur. The total number of normal individuals was only 32 of 

 the 125 or but 26^ , all others showing either autotomy or re- 

 generation or both. 



Of the 21 species, 14 or 67% showed autotomy. Those in 

 which it was not recorded being C. hucephalum, C. candelabrum, 

 C. heterocamptum, C. macroceros, C. seta, G. teres, and C. vidtur. 

 It has been seen by me, however, elsewhere in all these species, 

 but is more frequent in those with open tips, C. macroceros and 

 C. vultur. 



Of the 125 individuals 85 or 67% had undergone autotomy, 

 and it was more abundant, moreover, in those species of most 

 frequent occurrence. In the species represented by 4 or more 

 individuals, C. arcuatum, C. biceps, C. gallicum, C. inflexum, C. 

 intermedium, C. lineatum, C. longipes, C. protid)erans, and C. 

 tripos, were included 102 of the 125 individuals. The number 

 of these in which autotomy had occurred was 79, or 77.4%. It 

 is particularly frequent in C. intermedium and C. inflexum. 



Regeneration on the other hand was much less frequent, ap- 

 pearing, after autotomy, in only 19 eases or 15% and without 

 evidence of prior autotomy in but 6 cases or 5%. It is, perhaps, 

 significant that 17 of the 25 instances of regeneration occur in 

 three species C. gallicum, C. i^iflexum, and C. longipes, in all of 

 which autotomy is very frequent. 



To test the matter of the proportionality of the horns of in- 

 dividuals in which autotomy and regeneration or both have oc- 

 curred I have taken the first fifty individuals found by the aid 

 of the mechanical stage representing the following species, C. 

 gallicum, C. inflexum,. C. intermedium, C. longipes, C. carriense, 

 C. arcuatum, and C. biceps, merely omitting all normal ones after 

 the first. Measurements of the total lengths of the horns and of 

 their regenerated portions, if any. are given in transdiameters 

 at the girdle in the following table. 



