204 FILTER-BED NEMAS 



They appeared to have been feeding upon bacteria and other similar micro- 

 phytes. Monhysteras are more common in open filter beds and in reservoirs, 

 where they appear to feed principally on green unicellular algae, which naturally 

 do not flourish in covered filter beds, since sunlight, direct or diffused, is 

 necessary to their growth. 



IOTA Cobb 1913 



7. Iota simile, n. sp. ~ 8 79 o7~ ~7<)7s~^~i7I 676 ' 6 "" T ne colorless layers of 



the thick cuticle are traversed by ninety to one hundred plain, transverse 

 striae of such a nature as to give a relatively coarse serrate-crenate appearance 

 to the contour of the body. The annules of the cuticle are complete rings. 

 Only at rare intervals is there a trace of anastomosis; occasionally it will 

 happen that two semi-annules on one side of the body are joined to one on the 

 other. The convex-conoid neck ends in a somewhat rounded head surmounted 

 by a flat lip region composed probably of six very flat lips placed in the slightly 

 depressed front surface of the first annule. The first two or three annules are 

 packed closely together, and the prevalent crenate-serrate appearance of the 

 contour begins probably with the fourth annule, possibly with the third. No 

 labial papillae have been seen. Nothing is known concerning the amphids. 



Spear. The spear is rather more slender than in most Iotas, and tapers 

 throughout the main portion of the shaft, which constitutes fully two-thirds of 

 the length. Where it reaches its maximum development this shaft has a diameter 

 about half as great as the width of one of the neighboring annules of the cuticle. 

 Behind the shaft the hilt of the spear has a diameter only a trifle larger than that 

 of the main portion of the shaft. The hilt increases in diameter steadily 

 posteriorly, and finally expands suddenly into a large three-fold bulb nearly 

 one-fourth as wide as the corresponding portion of the neck. The central canal 

 of the spear is plainly visible, and is continuous with that of the oesophagus. 



Oesophagus and Intestine. The oesophagus is about as wide as the base of 

 the spear, and appears to present no very definite median bulb, though there 

 is a slight change near the middle of the neck which probably indicates the 

 position of some such structure. The details of the intestine are somewhat 

 obscure, but it appears to begin as a tube about half as wide as the body, and to 

 continue at this width for some distance. The anus seems to be located 

 between the fourth and fifth annules, counting from the posterior extremity. 

 The excretory pore is located near the twenty-sixth annule counting from the 

 head end where the annules first become distinctly developed; this means prob- 

 ably at about the thirtieth annule counting from the mouth itself. The tail is 

 conoid to the blunt terminus, which is destitute of a spinneret. 



Sexual Organs. The depressed vulva is located at about the seventh annule 

 from the caudal extremity. The vagina leads inward and forward a distance 

 fully equal to the corresponding body width. In front of this is the uterus, 

 which appears to be once and one-half to twice as long as the corresponding 

 body-diameter. The ovary extends directly forward and its blind end lies 

 some little distance behind the base of the neck. The eggs occur one at a time 

 in the uterus. They are thin-shelled, a little longer than the corresponding 

 body diameter and about half as wide as long. 



Habitat: Aberrant in filter beds, Washington, D. C. ; roots of grape-vine, 

 Herman, Mo. Synonymous with Iota are Ogma Southern and Criconema Hof- 

 manner and Menzel. Iota consists of many species. I have specimens and full 

 MS. descriptions of a number of new species collected during the last twenty 

 years in widely different parts of the world. All are -f and have the vulva 

 hidden among the annules near the anus; tiny, wide nemas with retrorse annules. 



