NEW TAPEWORMS FROM CARNIVORES SKINKER 213 



larium and in the number of testes), but the hooks are sufficiently 

 like those of the type specimen to leave no doubt concerning the 

 specific determination of this worm. Other strobilae collected from 

 the same host show in some of the mature segments much greater 

 similarity to the type specimen than do those that were photo- 

 graphed, but the condition of the material did not provide segments 

 suitable for photographing. The strobila of this larger worm ap- 

 pears to have been stretched in fixation, and this probably accounts 

 for the distance between the vitellarium and the posterior margin 

 of the segment as contrasted with the position of the vitellarium 

 in the type specimen. 



Male reproductive system. — Testes usually ^ spherical, sometimes 

 slightly elongated, 3(V to 50)U, in greater diameter in typical seg- 

 ments, 200 to 500 in number, with usual distribution between longi- 

 tudinal canals, not closely crowded in typical segment ; usually a few 

 testes in space between ovaries and vitellarium ; testes usually over- 

 lap lateral portions of vitellarium ; usually several testes posterior to 

 vitellarium, only rarely a few posterior to ovary. In plate 20, figure 

 2, are shown segments of a strobila in which testes are GO/a to 95)u, 

 in diameter and somewhat more crowded together. Seminal vesicle 

 not observed. Coiled mass of vas deferens passing in an approxi- 

 nuitely straight line from cirrus pouch toward center of segment. 

 Cirrus pouch 200ja to 375;u, long, TO/x to 110/^ wide, rarely extending 

 mediad to ventral longitudinal excretory canal. 



Female reproductive system.. — Ovaries varying somewhat in shape, 

 depending on state of contraction; typical shape of ovary is that 

 shown in plate 20, figure 2; each lobe wider (measured along trans- 

 verse axis of strobila) than long. Vitellarium usually of shape 

 shown in plate 20, figure 2, occasionally triangular, usually not ex- 

 tending laterad beyond lobes of ovary, about 1.5 mm wide as meas- 

 ured along transverse axis of strobila and about 120/x long as meas- 



^ The description of tbis species is based on the study of specimens collected over a 

 period of many years and therefore represents a far more extensive consideration of varia- 

 tion than is commonly included in the original description of a species. To one not 

 wholly familar with the usual variations found in cestodes, such a study has its disad- 

 vantages, for when one recognizes and tabulates variations resulting from different stages 

 of contraction and expansion (due usually to methods and media of fixation), from the 

 age of the specimens, from the size and state of nutrition of the host animal, or from the 

 multitude of undetermined factors (possibly the hereditary composite due to the genes) 

 that are accepted as playing a part in determining the physical characteristics of any 

 organism, it becomes difficult to set down concise statements concerning characters that 

 may be found in all specimens ; as a result the description lacks a pleasing exactness that 

 might be given to it if no note were made of these variations or if several additional 

 species were made on the basis of such variation. My study of cestodes has led me to 

 take the position that in many descriptions what has been designated as specific differ- 

 ences is no more than these individual variations, and with the resulting latitude given 

 to my conception of a species the frequent use of limiting adverbs such as " usually " 

 becomes unavoidable. 



