T^NIOID CESTODES OF NOETH AMERICAN BIRDS. 



31 



anatomy of the strobila shows the affinities of this sj^ecies with the 



ffeniis Rhabdometra. 



External anatomy. 



The length of this species, so far as could be judged from the 

 specimens examined, which were broken into small pieces, is about 

 75 mm. The maximum breadth of the strobila is 1.5 mm. The first 

 segments are very short (80 [x) and about 0.5 mm. broad, the oldest 

 segments slightly longer than broad, 0.95 to 1 mm. long by 0.85 to 

 0.95 mm. broad. The posterior border of each segment overlaps the 

 anterior portion of the following segment only very slightly. The 

 segments are nearly as broad at the anterior border as at the posterior 

 border and are hence nearly quadrate in shape. 



par . ut . 



d . ex . \ 



v.def . 



l.n. 



vag. 



" I sem.reeept. 



IOQm. 



Fig. 23. — RHABDOMETnA similis : Sexually mature segment becoming gravid, hori- 

 zontal SECTION, c. p.. Cirrus pouch, d. ex.. Dorsal excretory vessel. I. n.. 

 Nerve cord. par. ut., Paea-ltterine organ, sem. recept., Seminal receptacle, t.. 

 Testicles, ut.. Uterus, var/.. Vagina, v. def., Vas deferens, v. ex.. Ventral 

 excretory vessel, ij. (J., Yolk gland. 



The genital pores are irregularly alternate, located in the anterior 

 half of each segment. 



Internal anatomy. 



Nervous system. — The usual lateral longitudinal nerves (fig. 24, 

 I. n.) are present and are located a short distance beyond the most 

 lateral bundles of the inner longitudinal muscle layer, and inside 

 of the outer longitudinal layer, about equidistant from the lateral 

 border of the segment and the longitudinal excretory canals. 



Musculature. — The longitudinal muscles are arranged in two layers, 

 an outer layer of numerous small bundles and an inner layer of 

 larger bundles which are far apart and not over 20 to 24 in number. 



