UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 ZOOLOGY 



Vol. 3, No. 8, pp. 127-133 December 11, 1906 



ON THE SIGNIFICANCE OF THE ASYM 

 METRY IN TRIPOSOLENIA. 



BY 



CHARLES ATWOOD KOFOID. 



The appearance in Triimsolenia of an asjnnmetry caused by 

 the deflection to the left of the posterior ends of the antapicals 

 and a similar asymmetry in a number of species of Amphisolenia 

 (Kofoid :06) leads to a consideration of the significance of this 

 somewhat Avidespread phenomenon. Had it appeared as one of 

 the characters of a single species, or even of several, it would be 

 dismissed as one of those usual chance vagaries of structure 

 which so often crop out in the diagnostic features of a species. 

 Its occurrence in the two genera named and suggestions of an 

 analogous structural feature in some other genera of Dinoflagel- 

 lates is indicative of a more profound relationship to the welfare 

 of the organisms in which it appears. 



Locomotion in this genus, as in other Dinoflagellates, is 

 brought about by the combined action of the two flagella. The 

 transverse flagellum causes rotation about the antero-posterior 

 axis of the body, or rather about the axis of the spiral of progres- 

 sion, while the longitudinal flagellum is the principal organ of 

 propulsion, though it may also assist in the rotation. The com- 

 bined efl:'ect of the activity of the two flagella is to cause the 

 organism to move forward in a spiral course about a more or 

 less straight line of progression as shown in Fig. A. The rotation 

 may be in either direction, that is, dexiotropie or leiotropic. A 

 more precise definition of the motion is possible by using the axes 

 and poles of synnnetiy of the organism. The dexiotropie rotation 



