>24 



DEPTHS OF THE OCEAN 



and it is then quite evident that the direction and shape of the 

 horns may vary considerably from one generation to another. 



Fig. 22-J.—CERATIUM TRICHOCEROS. 

 Showing progressive and proportionate reduction of the horns in autotomy (^ f-). (Kofoid. ) 



0.0 



0.2 0-3 mm. U 



Fig. 228. — Ceratium platycorne. 

 , Forma cojnpressa ; 2, 3, forma normalis. 



In other cases, where the cells separate immediately after 

 division, it is more difficult to tell which variations are due to 

 hereditary dissimilarities and which are the result of direct 



