104 ASYMMETRY OF THE NEMATODE 



spicula are usually about two and one-half times as long as the anal 

 body diameter, and are accompanied by an accessory piece about 

 half as long, and arranged parallel to them. The spicula are more 

 or less cephalated by expansion. The accessory piece is usually quite 

 as conspicuous a feature as the spicula, since it is often slightly colored, 

 while the spicula are colorless. The male papillae are reminiscent of 

 those of Cephalobus. In the only males examined there appear to be 

 eight somewhat asymmetrically placed pairs, one pair opposite the 

 anus, two pre-anal, and five post-anal. These papillae are flattish, 

 innervated, minute, and inconspicuous. 



The young larvae of Bunonema do not bear tubercles. On the 

 species that bear them the tubercles become permanent elevations dur- 

 ing the last two moults. Just previous to the final moult they ap- 

 pear to be smaller and simpler than when fully developed. There is 

 little if any evidence on the right side of very young larvae of the very 

 remarkable transformation which is to take place in the course of growth ; 

 the cuticle differs from that of the left side so little that it is only by 

 careful scrutiny that the differences can be detected. There are no 

 reticulations and there is very little evidence of punctation. Previous 

 to the two last moults the cuticle of the right side is differentiated from 

 that of the left to a greater or less extent. Probably at the first moult, 

 the dexter cuticle becomes slightly thicker and almost imperceptibly 

 colored. The anal flap does not exist, or at least is in no wise promi- 

 nent, on young larvae. The cephalic setae and other cephalic organs 

 are neither so strongly developed, nor so complicated, on the larvae as 

 on the adults. 



When a specimen of Bunonema is mounted in water, with just suffi- 

 cient space between the coverglass and the slide for the nematode to 

 move about freely and without friction, it is seen to have the charac- 

 teristic movement of nematodes, that is to say, the normal flexures 

 of the body are in the dorso-ventral plane. This brings the tubercles 

 either squarely toward the observer, or squarely on the far side of 

 the body. At the same time the excretory pore, the anus and the vulva 

 come into exact profile. 



In manipulating specimens on the microscope slides it sometimes 

 happens that a tubercle is torn loose, and in such cases the tubercle 

 often comes off entire, as if there existed a definite junction along its 

 periphery, or at least as if the peripheral attachment were weak. 

 Such losses may in part account for the occasional irregular arrange- 

 ment of the tubercles. Specimens are not infrequently seen in which 



