2 PKOCEEDINGS OF THE ISTATIONAL MUSEUM vol.75 



INTERNAL MORPHOLOGY 



Nervous system. — The fairly f)rominent longitudinal nerves (fig. 7) 

 lie exterior to the excretory canals, and in cross section appear to 

 interrupt the inner layer of muscle-fiber bundles. 



Musculaim'6. — The longitudinal muscles (fig. 7) are arranged dis- 

 tinctly in an inner and an outer layer, each layer consisting of 

 numerous bundles of fibers, a total of 40 or more. Transverse and 

 dorsoventral muscles are but weakly developed. 



Excretory system. — There are the usual small dorsal excretory canal 

 and larger ventral excretory canal on either side (fig. 7). Anteriorly, 

 they are approximately the same size. The transverse canal in the 

 posterior portion of the segment is prominent, and a few supplemen- 

 tary transverse canals are observable, but these do not seem to make 

 up a reticulate system such as Ransom describes for another rhab- 

 dometrid, RJmdonietra nuUicoIlis. The genital canals pass between 

 the longitudinal excretory canals and dorsal to the longitudinal nerve 



(fig. 1). ^ 



Male reijroductlve organs. — The testes (figs. 5, 6, 7) are posterior 

 in the segment, and posterior and lateral to the ovary. They vary 

 in niunber from 12 to 25 in tlie segments of a single strobila, the 

 usual range being from 16 to 22. In no case were more than 25 ob- 

 served. Well-developed testes are usually transversely elongate and 

 measure about 75 by 45 ii. The vasa efferentia are indistinct; the 

 vas deferens is prominent and in the anterior portion of the segment. 

 The cirrus is comparatively straight in the cirrus sac, the straight 

 region being 160 to 180 /a long, and is armed with small spines for a 

 distance of about 60/.i from its tip. The large cirrus pouch (figs. 

 5, 7) passes median of the longitudinal excretory canals, and extends 

 diagonally toward the anterior portion of the segment. In mature 

 segments it varies from 195 to 225 \k long by 45 to 60 ;a wide, more 

 rarely to 300/^ by 52 to 60 ^i\ in gravid segments the cirrus pouch 

 (figs. 2, 4), though distinct, is usually smaller, ranging from 165 to 

 195 IX in length. 



Female reproductive organs.— T\\q vagina (figs. 5, 6) is posterior 

 and dorsal to the cirrus pouch. The enlarged distal portion, 135 to 

 195 IX long by 35 to 45 jm, wide, is followed by a narrow tubular proxi- 

 mal portion 4 to 6 jn in diameter, and that in turn by an ovoidal or 

 cylindrical seminal receptacle (figs. 5, 6, 7). The ovary (figs. 5, 6, 7) 

 is median (equatorial) or postmedian (postequatorial) in position, and 

 is bilobed when mature. The vitelline gland (figs. 5, 6) is posterior 

 and ventral to the ovary, and between them lies the small so-called 

 shell gland (fig. 7). The uterus (figs. 5, 6, 7), originally situated 

 anterior and dorsal to the ovary, invades and comes to occupy the 

 space previously occupied by the ovary before the latter degenerates ; 



