354 



BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



in species of Tetrameres. Cuticle transparent, finely striated trans- 

 versely, often projecting as the coils tighten. Anterior and posterior 

 extremities projecting to varying degree, never to a length of more 

 than half the diameter of the worm, and sometimes retracted into 

 the center of the coil. Buccal capsule dome-shaped. Esophagus 

 long. Intestine a black irregular tract, twisting with the coils. 

 Posterior extremity (fig. 416 /) sharply pointed; anus 450/*, vulva 

 900/x from the posterior end, cuticle thickened into a rounded swell- 

 ing between the two openings. Eggs 40 to 45 ju, long by 20 to 25/a 

 wide, containing coiled embryos when mature; some eggs show 

 peculiar unilateral bib attached to outside of shell (fig. 416 g). 



Fig. 416. — Microtetrameres contorta. a and b, Males ; c, yodngest 



FEMALE, SHOWING TENDENCY TO COIL ; d AND e, MATURE FEMALES ; 

 f, TAIL OF FEMALE ; (J, OVA, UNILATERAL BIB REPRESENTED ON ONE ; 

 h, MATURE FEMALE, SHOWING COURSE OF ESOPHAGUS AND INTESTINE ; 

 X, HALF GROWN FEMALE, COILED IN ONE PLANE ONLY. AFTER WEIDMAN, 



1913. j, Wax reconstruction of female. After Weidman, 1923 



Weidman made a very careful study of females of varying ages 

 (fig. 416 c to e and h to j) ; one of the wax reconstructions made by 

 him is shown in figure 416 j. He concludes that the propensity to 

 coil is of very early development. The arrangement of coils is not 

 constant, being either clockwise or contraclockwise. Head always 

 bent dorsally; posterior extremity always twists suddenly in direc- 

 tion opposite to that of anterior coils. With egg production the 

 coils broaden out so that the mass appears globular. 



Life history. — Probably similar in a general way to that of T. 

 flssispina (see p. 313). 



Distribution. — North America (United States (Pennsylvania 

 (Zoological Garden, Philadelphia)). 



