154 



ONYX AND DIPELTIS, 



Chromadora. The pharyngeal bulb is about one-fourth, the 

 posterior or cardiac bulb about two-fifths, and the intermediate 



canal about one-third as long as the 

 neck. While the cylindroid cardiac 

 swelling is three-fourths as wide as 

 the neck, the pharyngeal swelling is 

 only one-half and the intermediate 

 canal only one-third as wide as the 

 neck. The slightly oblique nerve- 

 ring has about the same width as the 

 oesophageal canal it surrounds, and 

 is accompanied by the usual groups 

 of nerve-cells. The tail is slightly 

 c onvex-conoid to the large conical 

 terminus, which begins with a slight 

 expansion. The widest portion of 

 the terminus is one-third as wide as 

 the base of the tail The caudal 

 glands are situated in the anterior 

 part of the tail, and are three in 

 number. The reflexed portion of the 



Fig. 8.— i, The Male of Onyx perfec- m t L 



tus(x40); ii, in, iv and v, the tail ovaries reach one-third the distance 



end, head, accessor y organs and 



anal region, respectively, of the to the vulva. 



same worm, more highly magnified now n».c mi 



(ii, x 750 ; in, x 225 ; iv, x 900 ; v, £_ h — »' 8 =» »« » 2 -l mm. The tail of 



x 175). In the anterior part of i . 2 ' 8 2 ' 9 3 3 3-3 3- 



the oesophagus is shown, surrounded the male closely resembles that 01 



by the nerve-ring (white); following ,, » i ,i i tzt -i • 



the oesophagus is the intestine, the the female, the only difference being 



view of which is interrupted near r -, , , £ 



the middle of the body by the an arcuate iorm and the presence ot 

 testicles (drawn lighter). an inconspicuous, low, broad, ventral, 



bristle-bearing papilla near the middle. The ventral series of 

 twenty to twenty-eight equi-distant accessory organs lies imme- 

 diately in front of the anus and occupies a distance a little more 

 than twice as great as the length of the tail. The linear spicula, 

 two-thirds as long as the tail, are cimetar-shaped, being of quite 

 uniform diameter. They are rather strongly and uniformly 

 arcuate in the distal four-fifths. The proximae are cephaloid by 

 unusually great expansion. The thin accessory pieces are one- 

 third as long as the spicula. 



