﻿544 GARRISON. 



apparent; lateral nerve trunks rather crescentie on cross section and measure 

 0.025 millimeter transversely by 0.150 dorso-ventrally in mature segments. 13 



Excretory system. — The ventral excretory canals pass in a straight course from 

 the head through the lateral borders of the strobila, at first ventrad to and later 

 directly in the median saggital plane. They attain their maximum diameter in 

 the first gravid proglottides (0.35 to 0.40 millimeter in median transverse plane) 

 and present a wide dilation (0.45 to 0.65 millimeter longitudinally by 0.80 to 0.90 

 millimeter transversely and dorso-ventrally) at each segmental junction. (Figs. 

 7, 8, 16. 17.) The transverse canals decrease in size as they pass inward from 

 the dilated portions of the ventral canals, are oval or diamond shaped on cross 

 section (figs. 5, 10) and are situated at the extreme posterior borders of the 

 proximal segments, it being impossible in either young, mature, or gravid pro- 

 glottides, to detect any extension of the proximal segment posterior to the canal. 

 (Figs. 5, 8, 13, 17.) 



The dorsal excretory canals can be traced as loosely wound, spiral tubules, 

 18 to 20 /j. in diameter, as far as the first sexually mature proglottides. The coils 

 of the spiral extend through a space of from 0.15 to 0.25 millimeter transversely 

 and dorso-ventrally and number five to six complete turns in each segment. 

 (Figs. 5, 7.) 



Genital organs. — The primordium of the vas deferens and vagina appears in 

 about the 150th segment, which measures 0.72 millimeter transversely by 0.24 

 millimeter longitudinally, and is situated 12 millimeters from anterior extremity. 

 At about the 300th segment (1.75 millimeter by 0.45 millimeter, 2 centimeters 

 from anterior extremity) the uterine stem is present as a distinct tract beginning 

 posteriorly in the bulbous mass at the median extremity of the vagina, and 

 passing diagonally anterolaterally toward the pore side of the segment until it 

 reaches the angle between the vagina and vas deferens, which are now separated 

 throughout the inner half of their course ; thence turning at an acute angle, it 

 takes an antero-median course to the median line, and along the median line to 

 the anterior border of the segment. (Figs. 6, 7.) In the 400th segment (3 

 millimeters by 0.64 millimeter, 6 centimeters from anterior extremity) the female 

 organs have became differentiated into the ovarian lobes and vitellogen gland, 

 the testicles are appearing in lateral fields of medullary layer, the cloaca is 

 forming at the lateral margin, the Y-shaped course of the uterine stem in the 

 posterior half of the segment is more sharply defined and its anterior prolonga- 

 tion in the median line is coiled in one or two loose spiral turns. The 475th 

 proglottid is sexually mature. (Figs. 8, 10.) 



Sexually mature proglottid. — Measurements : 5 millimeters transversely by 1 

 millimeter longitudinally by 1.35 millimeters dorso-ventrally, situated 15.5 cen- 

 timeters from anterior extremity of specimen. Genital pore slightly posterior to 

 middle of lateral margin (fig. 8) ; cloaca 0.32 millimeter deep (figs. S, 12, 15) ; 

 cirrus 0.1 millimeter long by 0.03 millimeter broad (fig. 15) ; cirrus pouch 0.35 

 millimeter long by 0.1 millimeter broad (fig. 15) ; vas deferens makes distinct 



13 In the absence of specific staining for the nerve tissues, the nature of the 

 globular structure in the posterior part of the head can not definitely be deter- 

 mined. The interpretation here made is based upon the marked similarity in 

 appearance and structure in cross section between the lateral nerve trunks and 

 the body in question when stained with carmine, upon the faint tracings of what 

 appear to be nerve trunks arising from it. upon its position, and upon the 

 elimination of other possible interpretations. The presence of a large, globular, 

 well-defined ganglion as the center of the nervous system instead of the usual 

 commissural arrangement of fibers would be an important character, but in view 

 of the uncertainty of interpretation, it is not included in the diagnosis. 



