164 ILLINOIS BIOLOGICAL MONOGRAPHS [452 



ma collocati a destra o a sinistra die essa formando in tal modo une striccia a 

 zig-zag. 



L'aperture genitale maschile sbocca sulla faccia dorsale, e sulle opposta si 

 apre I'utero. In alcune proglottidi I'ovario e bilobo, la uova sono ellissoidali e 

 mancano di operculo. " 



Liihe (1899:42-44) in defining the characters of the genus gave the general 

 features of the genitaUa, while Ariola (1900:397) enlarged his own 1896 des- 

 cription: "Ovario con numerose uova, talora bilobo; uova eUissoidaU aventi 

 nel diametro longitudinale 61 n e nel trasversale 32. ..." Braun (1900) 

 reviewed the literature on the genus and species up to date, and Volz (1900) 

 discussed the reproductive organs of the species as compared with those of his 

 B. spiraliceps and the position of the openings in connection with brief remarks 

 on the phylogeny of the genus Bothriocephalus s. lat. As regards his own speci- 

 mens Linton (1901:473) said that "Posterior segments show rudiments only 

 of the reproductive organs, but no indication of external genital openings." 

 And later Johnstone (p. 89) remarked that "the genital openings are in the 

 middle Hne of the proglottides but near the anterior borders of the latter," 

 referring evidently, as will be seen later, to the uterine openings only. 



The rudiments of the reproductive organs appear about three millimetres 

 from the tip of the scolex as aggregations of nuclei that can just be discerned 

 in toto mounts (Fig. 48). About three millimetres farther posteriorly in mod- 

 erately contracted older strobilas (such as would be obtained if no special care 

 were taken during the fixation of the material) the cirrus and vagina are seen 

 to be just piercing the dorsal surface. Before this region is reached, however, 

 the common rudiment, at first circular and then elongated oval in outline, 

 differentiates into a more anterior portion, the rudiment of the whole uterus, 

 a more posterior less elongated part, the beginnings of the cirrus-pouch and 

 vagina, and a third, connecting the other two near the hinder edge of the 

 proglottis, the nuclear aggregation that will develop into the ovaries and the 

 organs of the interovarial space (Fig. 74). As mentioned in the specific diag- 

 nosis, the first two of these rudiments alternate irregularly from side to side 

 as do the corresponding adult structures. At the same time the testes and 

 vitelline glands are developing in the medullary and cortical portions of the 

 parenchyma, respectively. 



A distinct genital sinus or cloaca, the opening of which is usually almost 

 circular in outUne, is present (Fig. 75). It varies from 0.05 to 0.09mm. in 

 diameter and is situated, as above noted, nearly in the median line, dorsally, 

 and from three-fourths to one-half the length of the proglottis from its anterior 

 border, usually just posterior to the spurious articulations when they are 

 present. At the bottom of this sinus there is a secondary cloaca ("Gesch- 

 lechstasche" or "Ductus hermaphroditious"), also circular in outhne, from 15 

 to 25m ill diameter, and into it open the cirrus and vagina quite close together, 

 the latter immediately behind the former. This secondary sinus is best seen 

 in sagittal sections (Fig. 103). The genital pore (the opening of the main 

 sinus) is elevated sUghtly above the general dorsal surface of the proglottis, 



