14 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



the two bothria, which, lying back to back, constitute a lateral 

 pair. These lateral vessels form close spirals near the base of the 

 scolex, where they are joined by the axial vessels to continue in the 

 strobile as the dorsal and ventral lateral vessels. 



There are two layers of longitudinal muscles, arranged in bundles, 

 the outer layer consisting of many small bundles each containing few 

 fibers, the inner layer consisting of fewer and larger bundles. In 

 proglottides in which the uterus was rudimentary the outer bundles 

 contained a maximum of about 30 fibers, the outer bundles about 7. 

 In proglottides in which the uterus was well advanced, the inner 

 bundles contained a maximum of about 20 fibers, the outer about 5. 

 At the base of the scolex there is but a single layer of longitudinal 

 muscles, which is separated from the cuticle by a granular layer 

 containing many radial fibers. Near the scolex the layer of circular 

 fibers, which encloses the medullary space, is conspicuous. It becomes 

 less so in older portions of the strobile. Longitudinal sections give 

 no indication of the formation of free proglottides. A tendency to 

 separate from the strobile was observed only in the case of the 

 slender variety. 



RECORD OF COLLECTIONS 



Gavia imnier: 



(U.S.N.M., Helm. Coll. 7863.) 



1906, January 8. — Two loons examined; 12 tape worms in one, 

 30 in the other. 



1911, July 1. — Fourteen large, with adult, loose proglottides, 

 length 125 mm.; 6 small, also with loosening proglottides, 

 length 10; 1, length 30. 



1911, July 22. — Twent3'^-one large and small, with fragments; 

 maximum length 100 mm., in alcohol. 



1911, July 24. — One hundred and forty-seven scoleces and 77 

 strobiles and fragments without scoleces. There were two 

 varieties, one relatively thick, much longer and larger than 

 the other, which is slender and filiform. One of the larger 

 measured 125 mm. when straightened in a dish and fixed in 

 corrosive acetic. One of the smaller, slender strobiles meas- 

 ured 30, and another 45 mm. in length. There were interme- 

 diate forms, so that it would appear that these seemingly dif- 

 ferent forms simply represent different ages of strobiles of the 

 same species. There is not a corresponding difference in the 

 size of the scoleces. 



1911, September 1.— About 20. 



1913, January 1. — Twenty-three with scoleces; the largest stro- 

 bile noted was 100 mm. in length, and 2.5 in greatest breadth, 

 in formalin; scoleces large, length 1.12, breadth 0.84; ova with 

 six-hooked embryos. 



