182 ILLINOIS BIOLOGICAL MONOGRAPHS [470 



both dorsally and ventrally. Right and left vitelline ducts passing to the 

 median line close to the ventral layer of transverse muscles unite ventrally 

 to form a common duct, which acts as a yolk reservoir. The imion of the 

 common vitelline (Fig. 109) duct with the oviduct takes place in the median 

 frontal plane, a Httle aside from the median line and just beyond the bend in 

 the oviduct before which is located the point of union of the vagina. The 

 shell-gland is quite compact and situated close to the dorsal wall of the medulla. 

 The uterine duct takes only a very few short coils, mostly in the dorsoventral 

 direction close to the median line, before passing into the very capacious uterus- 

 sac. The latter vies with the large ovary in filling up the median portion of 

 the medulla, and measures in mature (not gravid) proglottides, 0.74mm. wide, 

 0.74 long and 0.37 deep, being ob\dously quite flattened in the antero-posterior 

 direction as are the other organs. In mature proglottides which are quadrate 

 in shape it may be still somewhat elliptical in outline, as much as 1.6mm. long by 

 1.3mm. wide, and show distinct lobations; whereas the widest and most gravid 

 joints may be Httle else than sacs of eggs, the rest of the reproductive system 

 in both cases having almost entirely degenerated. The uterus-sacs were con- 

 stantly found to be rounded or lobate laterally, as stated by Matz and Liihe. 

 The openings form a somewhat irregular zig-zag row on the ventral surface 

 of the strobila, without, however, being accommodated in a distinct groove. 



The eggs, taken from gravid uteri and measured in the formalin in which 

 the strobilas were preserved, were, externally, 80 to 98)u long by 75 to 92 wide; 

 mantle, 67 by 62/:; "ectoderm " (of Schauinsland), 62 by 54/i; and oncosphere, 52 

 by 40ju. The similar data given by Dujardin, which were considered by Lin- 

 stow to be not of this species, were: shell, 80 to 110 by 50 to 57^4; "ectoderm," 

 or inner shell, 51 to 57/i; oncosphere, 48 to 50/i. Linstow's figures, copied by 

 Liihe, were 59 by 43a£. 



The earUest stages in the development of this species have long been known 

 from the work of Schauninsland (1885:527), who followed it to the escape of 

 the oncosphere enclosed in the non-ciliated mantle. Saint Remy (1900:296-7) 

 thought that he probably saw polar bodies and the male and female pronuclei 

 among other important finds, and came to the conclusion "... que les 

 phenomenes sont essentiellement les mdmes chez les Bothriocephales et chez 

 les Taenia et se resument dans la constitution de deux enveloppes autour de 

 I'embryon hexacanthe." Olsson found a small strobila 22mm. in length in 

 Gadus aeglifinus, which he considered to belong to this species; but apart from 

 this there seem to be no other references in the literature to the development 

 of the strobila from the plerocercoid. As stated above, the smallest found by 

 the writer was also 22mm. in length, but no such invagination of the scolex as 

 mentioned by Olsson was observed. 



As stated above, there is considerable evidence in the literature of this 

 species to indicate that the form found in marine Gadidae and called A . gadi 

 by van Beneden (1871:56) is not the same as that found in the only fresh- 

 water gadid, viz., Lota. In endeavoring to place a number of specimens from 

 Lota maculosa, it was found that in many points they agreed with the descrip- 



