UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 ZOOLOGY 



Vol. 3, No. 7, pp. 1 17-126 December 11, 1906 



A DISCUSSION OF SPECIES CHARACTERS 

 IN TRIPOSOLENIA. 



I. — The Nature of Species Characters. 

 II. — The Adaptive Significance of Species Characters. 

 III. — The Coincident Distribution of Related Species. 



BY 



CHAELES ATWOOD KOFOID. 



/. The Nature of Species Cliaracters in the Genus Triposolenia. 



The genus Triposolenia is sharply set off from other genera 

 of the Dinophysidae by the pronounced form of its midbody and 

 the relation which this bears to the balanced antapical horns and 

 to the anterior process. As yet no species have been found which 

 will afford a transition between Triposolenia and the most nearly 

 related genus Amphisolenia which has a fusiform midbody and a 

 single simple or branched antapical horn. 



The characters by which the species of Triposolenia may be 

 distinguished from each other are principally the form of the 

 midbody, the origin of the antapical horns, as well as their curv- 

 ature, spread and tips, the curvature and obliquity of the neck, 

 and the shape of the head, especiall}^ of the epitheca. The struc- 

 tures least modified are the anterior process, the lists and collars. 



Differentiations of the thecal wall appear only in T. truncata. 

 Differences in position of nucleus and vacuoles and in the num- 

 ber, form, and color of the chromatophores and plasmosomes 

 appear to have little significance in the matter of specific dis- 

 tinctions. 



