^°^- ^] Kofoid. — Triposolenia. 97 



species except those with pendant midbody. The slight inequal- 

 ity of the sides is constant in that the antero-ventral margin is in 

 all species the shortest and the post-margin the longest. This 

 inequality results from the fact that the anterior process in all 

 species has its origin on the ventral side of the axis of the mid- 

 body. 



The species of Triposolenia fall in two distinct groups or sub- 

 genera with reference to the form of the midbody. In the tnin- 

 cata group (Subgenus Posterocorma) the margins of the mid- 

 body are approximately equal and the horns originate on the 

 posterior angles. In the ramiciformis group (Subgenus Bamici- 

 formis) the two anterior margins are very unequal, the antero- 

 dorsal being the longer and nearly horizontal, the antero-ventral 

 being practically obliterated, while the post-margin is extended 

 in a pendant lobe with oblong or subrectangular outline. The 

 nucleus and the greater part of the protoplasm of the organism 

 is found in this pendant region. 



The anterior process [a.p. PL 15, fig. 1) is an extension of the 

 midbody in the antero-ventral direction at an angle of 10°-20° 

 from the axis. Its length does not exceed and is usually less than 

 the altitude of the midbod3^ It is a stout, laterally compressed 

 process about twice as thick dorso-ventrally as the neck. It ex- 

 pands abruptly on -the ventral side at the cytopharynx {c'pli. 

 PI. 15, fig. 2) about the flagellar pore {f.p. PI. 16, fig. 6). Its 

 point of origin in species with pendant midbody (PI. 17, figs. 

 7, 8) is shifted to the ventral side so that the ventral horn and 

 anterior process bifurcate from a common projection of the mid- 

 body. 



The neck (n. PI. 16, fig. 6) is a slender cylindrical extension 

 of the anterior process, whose length to the base of the head is 

 0.8-1.75 of the altitude of the midbody. It is straight or curved 

 dorsally, of uniform calibre throughout or constricted distally 

 (PI. 17, fig. 7) and is more or less, 10°-35°, deflected dorsally 

 from the axis. It passes abruptly into the expanded head just 

 below the posterior collar of the girdle. 



The liead {hd. PI. 15, fig. 2) is composed of the epitheca and 

 the expanded region at the end of the neck. It is encircled by 

 the broad transverse furrow which covers nearly two-thirds of its 



