260 ORDER ISOLAIMIA 



applied part one-third as long as the spicula, and projecting at right angles to 

 this is a uniform, blunt apophysis, one-half as long as the anal body-diameter 

 having its proximal end opposite the axis of the tail. The testes are wide and 

 more or less tapering. 



Habitat: Key West and Biscayne Bay, U. S. A., on algae. Flemming to glyc- 

 erine jelly. Fig. 42, p. 259. 



43. Rhynchonema cinctum n. sp. Annules of the cuticle retrorse posteriorly, 

 the reverse anteriorly. Neck cylindroid, very rapidly narrowing just behind the 

 head, and thence nearly cylindroid, so that the entire head 

 qJlsetUOl forms a kind of flexible beak. There are no eye-spots. Co- 

 tstibcph n id oesophagus at the nerve-ring two-fifths, and finally one- 

 half, as wide as the corresponding part of the neck; it has a 

 (" fine colorless musculature with no indication of glands. The 

 lining is indistinct. There is no cardia. The intestine, set 

 off by a collum one-fifth as wide as the neck, becomes at once 

 three-fourths as wide as the body. It has a distinct refrac- 

 5) 7 3 16 25. '-72 89. tive lumen and is thick-walled; its cross-section 



'(.8)'i.V "i5' : "3-V " '3.4 '2:9 presents two to three cells. From the continu- 



(.5) 7.4 16. 26. *-M 87. > 5 us anus, the rather inconspicuous though 

 '(.9) 'i.V ' 3-3' '3.'?' ' ' j.j'f^M cutinized rectum is three-fourths as long as the 

 anal body-diameter. Only the first few cells of the intestine show granulation. 

 The conoid, sub-arcuate tail tapers from the anus to the non-striated spin- 

 neret, whose width is about equal to that of three of the caudal annules. At 

 the base of the spinneret there are always about three minute nuclei that stain 

 strongly. The ellipsoidal caudal glands form a close tandem in the anterior 

 two-fifths of the tail. The lateral fields are about one-third as wide as the 

 body, but are more or less indistinct. Renette unknown. In the vicinity 

 of the vulva about eight of the annules present simply a crenate, instead of 

 a serrate contour. The broadly elevated vulva is rather conspicuous, particu- 

 larly in front. Vagina small. A mass of small sperm cells has been noted near 

 the vulva. The eggs are about eight times as long as the body is wide and one- 

 twelfth as wide as long. They are granular ^and have a prominent central 

 nucleus. The narrow cylindroid ovaries contain ova arranged single file. The 

 spicula of the male, about as wide as one of the adjacent annules, are slender, 

 rather frail, and sub-acute, and when seen in profile appear to have their proxi- 

 mal ends about opposite, or a little dorsad from, the body-axis. There is a 

 slender, frail accessory piece. The three minute papilloid supplementary organs 

 occupy a space three times as great as the body-diameter, and are about one 

 body-width apart; the posterior member is about two body-widths in front of 

 the anus. They hardly more than accentuate the annules on which they occur, 

 but are rendered visible by carmine stains. The ejaculatory duct is one-fourth 

 as wide as the corresponding portion of the body, the cylindroid testis one-half 

 as wide. 



Habitat: Salaverry, Peru, near low tide mark; marine. Rhynchonema is com- 

 posed of a considerable number of species occurring in at least the Atlantic and 

 Pacific Oceans. With low powers it is difficult to distinguish the head end from 

 the tail end. The flexible, narrow head suggests the functions of a beak. One 

 may imagine it to probe the depths of some receptacle containing food, for 

 instance the neck of an algal oogonium. However, nothing is known with cer- 

 tainty concerning the food habits. Fig. 43. 



