208 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



tentacle of Pavillardia and Enjihroims^ and is not a modified flagellum. 

 The order Cystoflagellata is not required for Noctiluca ; it may remain 

 in the meantime for Leptodiscus and Oraspedotella. The structure of 



*'"- — - postp. 



long, fl 



A typical dinoflagellate, Gyrodinium corallinum g. et sp. n. 

 (Kofoid and Swezy MSS.). x 600. 



■Ant.p,^ anterior pore; epi., epicone ; qir., girdle; hyp., hypocone ; 

 interc.a., inter-cingular area ; long.fl., longitudinal liagellum ; n.., 

 nucleus ; pig., pigment ; post. p., posterior pore ; pus., pustule ; sulc, 

 sulcus ; tr.fi., transverse flagellum. 



Noctiluca should be compared with that of a typical dinoflagellate (see 

 figure), with sulcus, girdle, and flagella, but it has no theca or cuirass. 



J. A. T. 



Renewal of Vitality through Conjugation. — Gary N. Calkins 

 {Joum. Exper. Zool., 1919, 29, 191-56, 1 chart, 1 fig.). In the hypo- 

 trichous ciliate UrolejHus mobiUs the processes of metabolism are not 

 capable of unlimited activity. The limits vary from 'iiJS to 349 genera- 

 tions after conjugation or encystment. There is an optimum during 

 the first tliree montlis after conjugation, and then a progressive and 

 cumulative weakening of metabolic vigour, leading to death. Conjuga- 

 tion, however, changes the protoplasm from metabolic weakness to 

 optimum vigour. There is a limit to tlie extent to wliich the pro- 

 toplasm can be rejuvenated. It seems as if the protoplasm could hold 

 only a certain charge, so to speak, or potential of metabolic vigour, as a 



