PAFATYLENCHUS 



369 



dorsad and occupying the major part of it, and emptying into the oesoph- 



rl lumen near the onchium. It is doubtful if salivary secretion passes 

 into the base of the fusiform median valve, though there seem to be two 

 subordinate nuclei in the cardiac swelling. 



There is no cardia. The thick walled intestine, set off by a rather 

 faint cardiac collum one-half as wide as the base of the neck, presents a 

 faint, though fairly capacious lumen. It is composed of cells of such a size 

 that probably only about two are presented in each cross section. It becomes 

 at once two-thirds as wide as the body. From the very inconspicuous, con- 

 tinuous anus, the rectum, which is also very inconspicuous, extends inward 

 and forward. There is no distinct pre-rectum. The numerous, colorless 

 granules found in the cells of the intestine, the largest of which are about one- 

 tenth as wide as the body, namely about two microns in diameter, are not so 

 arranged as to give rise to a tessellated effect. Sometimes the cells throughout 

 the intestine are uniformly filled with granules ; more often the granules are 

 absent here and there, so as to create a "segmented" effect. 



The tail, which compasses about twenty annules of the cuticle, is conoid, 

 subarcuate, and tapers from in front of the anus to the rather blunt, or some- 

 times subacute, unarmed, symmetrical terminus. There is no spinneret. 

 There are no caudal glands and there are no caudal setae. 



Apparently the lateral chords are about one- 

 third as wide as the body. The rather prominent 

 excretory pore is located just behind the nerve ring 

 and the excretory duct can be followed inward and 

 backward along the right lateral chord at least as 

 far as the middle of the body. 



The nerve ring is oblique, of medium size and 

 accompanied, fore and aft, by numerous nerve cells, 

 some of which lie as far forward as opposite the 

 middle of the median oesophageal swelling. 



The single female sexual organ is outstretched 

 forward. From the unusually large, depressed and 

 very conspicuous vulva, the vagina, which is large, 

 extends inward obliquely forward, three-fourths the 

 distance across the body. Its walls are rather 

 strongly cutinized. The larger anterior lip of the 

 vulva may be slightly elevated. The body of the 

 nema decreases a little in diameter rather suddenly 

 at the vulva and tapers more rapidly thence back- 

 ward. The thin-shelled, smooth, elongated egg is 

 nearly thrice as long as the body is wide and meas- 

 ures about 60 x 20 microns. Only one egg occurs in 

 the uterus at a time. A prolate compact mass of 

 sperm cells, often comprising some two to five hun- 

 dred minute, spherical, refractive elements, occurs 

 regularly in the uterus of newly adult females; this 

 sperm mass is often two-thirds to three-fourths as 

 wide as the body. From the formation and size of 

 the sperm cells it is concluded that the species is 

 syngonic. No males have been seen among about 

 fifty females, many gravid, from two North Ameri- 

 can regions. The medium sized ovary is usually 

 cylindroid posteriorly, and tapers anteriorly; it aver- 

 ages to be about one-third as wide as the body. 

 Toward fifty ova, arranged for the most part sin- 

 gle file, are to be seen in the ovary. There is prac- 

 tically no post-vulvar rudiment of a sexual organ. 



grnmt; 



1. Anterior part of a 

 Paratylenchus nanus. 



