FREE-LIVING FRESH-WATER NEMATODES 73 



APHANOLAIMUS, de Man, 1880. 

 Fig. 25, Plate VIII. 



43- 

 .5 8.8 20. '50.' 88. 



22. Aphanolaimus spinferus, n.sp. - 1.5 mm 



.7 1.5 2.1 3.1 1.9 



The thin, transparent layers of the colorless, naked cuticle are traversed 

 by about one thousand transverse striae, which do not appear to be further 

 resolvable, or at any rate are resolvable with difficulty. The cuticle is also 

 traversed by longitudinal striations, manifestly due to subcuticular struc- 

 tures, the submedian fields and the attachment of the muscle cells. The 

 contour of the body is minutely crenate. There is .a distinct wing extending 

 throughout the length of the body, whose presence is indicated by two re- 

 fractive lines occupying a space hardly greater than the width of one of the 

 annules of the cuticle. On being carefully examined these lines show traces 

 of the striations of the cuticle. The conoid neck ends in a somewhat rounded 

 head, whose lip region is set off by a minute constriction just in front of 

 the amphids. The contour of the front of the head is rounded, or, like 

 that of a very flat truncated cone. In the midst of the truncation there is 

 an exceedingly minute depression, the mouth pore. There does not appear 

 to be any very distinct pharynx, but the lining of the oesophagus is slightly 

 altered in the region of the head back as far as the posterior margins of the 

 amphids. It is not unlikely that this represents a distinct, though rudi- 

 mentary pharynx. The species, however, would naturally at first sight be 

 classed as being without a pharynx. The oesophagus begins as a tube about 

 half as wide as the base of the head, and expands very gradually until after 

 it passes through the nerve-ring. At the nerve-ring its width is about one- 

 third that of the corresponding portion of the neck. Behind the nerve-ring 

 the oesophagus begins to expand a little more rapidly, though still slowly. 

 When it reaches the end of the neck it is half as wide as the base of the 

 neck. For a distance equal to one body diameter, however, it decreases in 

 size, so that where it joins the intestine it is very narrow, only about one- 

 fifth as wide as the corresponding body diameter. Nevertheless, there ap- 

 pears to be a distinct, though exceedingly minute cardia. The lining of the 

 oesophagus is a fairly distinct feature throughout its length. The intestine, 

 which is at first thin-walled, gradually becomes half as wide as the body, and 

 is composed of cells of such a size that only two or three are required to 

 build a circumference. For the most part the wall of the intestine is moder- 

 ately thick. From the very slightly raised, rather inconspicuous anus the 

 slender rectum, which is about one and one-half times as long as the anal 

 body diameter, extends inward and forward. It is separated from the in- 

 testine by a very distinct and deep constriction. Near the middle the lateral 

 fields are about one-third as wide as the body. The ventral gland is a rather 

 elongated, saccate cell a little longer than the base of the neck is wide, 

 and about one-third as wide as long. It contains a large spherical nucleus, 



