617 



Affinities. — This species is easily distinguished from the other 

 species of the genus. It resembles F. agilis Smith ('95, p. 288), 

 F. longa Moore ('95, p. 341), and F. ratscli Eisen ('72, p. 123) 

 more closely than it does other members of the genus, but it differs 

 from F. agilis in the number of set?e per bundle, the number of 

 diverticula on each spermatheca, and in the characters of the ne- 

 phridia. It differs from F. longa in the characters of the setse, pep- 

 tonephridia, and spermathecae ; and from F. ratscli in size, and in 

 the characters of the brain and the spermathecas. 



EXTERNAL CHARACTERS 



The body is long, slender, and cylindrical. The average length 

 is about 30 mm., the extremes being 24 and 33 mm. The diameter 

 is greatest at the clitellum (0.6 mm.), gradually decreasing both 

 caudad and cephalad. The intersegmental grooves are rather ob- 

 scure except in the region just posterior to the prostomium, where 

 a few are cjuite distinct. No secondary annulations are present. The 

 number of somites varies from 62 to 67. The prostomium (PI. 

 XCVIII, Fig. i) is blunt and rounded. The seta bundles in the an- 

 terior part of the body each contain 6-7 setae ; those in the posterior 

 part 2-4 each. The proximal ends (PI. XCVIII, Fig. 2), especially 

 of the more fully developed setce, are strongly bent. 



INTERNAL CHARACTERS 



Body Wall. — The cuticula, though comparatively thin, is tough 

 and firm, and offers the chief difficulty in the dissection of alcoholic 

 specimens ; but when once broken, it can be easily stripped from the 

 body. It has a luster, in both surface and sectional views, which 

 gives it a glistening appearance. It is oi about the same thickness 

 throughout the length of the body. It is reflected into the mouth and 

 lines the digestive tract as far as the openings of the peptonephridia, 

 being continued into the latter for a short distance. It lines the 

 canal of the head pore for most of its length, but is merely perforated 

 at the dorsal pores. The comparative thinness of the cuticula is 

 probably attributable to the fact that this species lives in moist earth. 

 According to Vejdovsky ('79, p- n) such forms as AnachcEta,\\h\z\\ 

 live in dry surroundings, have a very thick cuticula, while in those 

 living in water or in very moist earth it is thin and delicate. It was 

 noticed that the mortality in this species was very high when the earth 

 surrounding the specimens approached dryness, or when they were 

 exposed for a short time to the open air. 



