164 ILLINOIS BIOLOGICAL MONOGRAPHS [452 



ma coUocati 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-M) in defining the characters of the genus gave the general 

 features of the genitalia, while Ariola (1900:397) enlarged his o\\ti 1896 des- 

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

 nel diametro longitudinale 61 ii 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 \\dth brief remarks 

 on the phylogeny of the genus BolhriocepJialus s. lat. As regards his cmn 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 line of the proglottides but near the anterior borders of the latter," 

 referring evidently, as v,'ill be seen later, to the uterine openings only. 



The rudiments of the reproductive organs appear about three milhmetres 

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

 in toto mounts (Fig. 48). About three millunetres 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 rudimicnt, 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 tim.e the testes and 

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

 parenchyma, respectively. 



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

 circular in outhne, 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 outline, from 15 

 to 25/x in 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 shghtly above the general dorsal surface of the proglottis, 



