1908] Kofoid. — ExtmiatioH and Autotomy in Ceratium. 383 



off Coronado Pier had a temperature of 20.8°. Temperature of 

 water off San Diego pumped from a depth of 70 fathoms on 

 June 30, 1903, was 14.2°, on Jiily 1 was 14.7°, on July 2 from 

 72 fathoms, was 15°, on July 3 from 70 fathoms, was 14.7°, on 

 July 7 from 72 fathoms was 15°, and on July 9 from 72 fathoms 

 was 15.5°. It is possible that the extreme limits from which this 

 particular specimen might have been taken lie approximately be- 

 tween about 14° and 20.8°. If it had taken on its new growth 

 to adjust its flotation in water which had risen to 20.8°, the 19% 

 increase in specific surface would, according to Ostwald 's ( :03, 

 p. 62) table of temperatures and molecular friction, accommodate 

 the organism to an advance from 12.25° to 20.8°, or to a rise of 

 8.55° Tests of vertical distribution of temperature made off 

 San Clemente Island in July, 1905, with the self-closing water 

 bottle (see Kofoid :05) indicate that a decline of temperature 

 to this extent occurs within approximately 200 fathoms of the 

 surface. This distance, 200 fathoms to the surface, is quite 

 within the range of the possible distribution of this organism. 

 This is a somewhat close approximation between the increase in 

 specific surface caused by the renewed growth and the changes in 

 molecular friction due to the range of temperatures in the possi- 

 ble habitat of the species. This close agreement between Ost- 

 wald 's experimental determinations and my computations of the 

 changes in specific surface of this pelagic organisms are all the 

 more striking and significant if the probability of error in the 

 determination of the specific surface of so small and irregular a 

 body as that of C. califoritiense is borne in mind and also the 

 certainty that other factors enter to modify the process of adjust- 

 ment, such as alterations in specific gravity which might follow 

 from changed proportions of thin and thick thecal wall, and from 

 modifications in metabolism and in cell contents attendant upon 

 increased illumination and reduced pressure. 



Summary. 



In some Dinoflagellata ecdysis, or the shedding of the total 

 exoskeleton does not occur. 



In those genera, such as Ceratium, in which the theca is shared 

 between the daughter schizonts at schizogony, compensatory re- 



