378 University of California Publications in Zoology. [Vol. 4 



generation of the horns. Ceratium exhibits, however, the capac- 

 ity of increasing the length of its horns quite apart from aiito- 

 tomy. In species of the C. macroceros group in which the antap- 

 ical horns have open tips the horns increase in length by simple 

 extension of the protoplasm and its accompanying wall. In 



Fig. 28. — Dorsal view of Ceratium lamellicorne (nomen novum = C. tripos 

 forma dilatata Karsten ^ C. dilatatum (Karsten) Kofoicl) showing renewed 

 growth of the apical horns. X 440. 



Fig. 29. — Dorso-lateral view of Ceratium reticulatum spiraJe showing the 

 same. X 100. 



Fig. 30. — Ventral view of Ceratium divaricatum, showing regeneration 

 of all three horns after basal autotomy. X 100. 



figure 27 are shown individuals of C. intermedium and C. osten- 

 feldi (?), in which all these horns are thus being extended ap- 

 parently after autotomy, for, with this extension the total length 

 is still within the norm of the species. The regenerated parts are 

 exceedingly thin-walled and have apparently just formed and not 



