116 ILLINOIS BIOLOGICAL MONOGRAPHS [116 



Von Linstow states that there are about 25 testes in each segment, 

 and that these are situated in two fields near the vitellaria. In a draw- 

 ing of a transverse section, reproduced (Fig. 168), von Linstow figures 

 the testes in two layers. This causes the writer to suspect that the 

 number of testes (25) as stated by von Linstow is too small. In all the 

 species of Proteocephalus studied by the writer the testes have been in 

 one layer if the number of testes was small and never in two layers 

 unless they numbered at least fifty. Frequently one sees proglottids 

 containing more than fifty testes lying in a single layer. It should also 

 be borne in mind that von Linstow figured ten testes in his cross-section 

 of the proglottid. Ten out of twenty-five is too large a proportion of 

 testes to appear in one thin section through proglottids of this size. One 

 wonders what was left for the other sections of which there must have 

 been quite a number. Since the proglottid which von Linstow delin- 

 eates is ripe or at least contained eggs in the uterus it seems probable 

 that he overlooked the testes of the median region where the eggs would 

 be densely packed. In the transverse section to which reference has 

 been made the region dorsal to the coils of vas deferens is free from 

 testes, a condition which exists in all the other species of the genus 

 whether the number of the testes be few or many. If von Linstow 's 

 statement that the testes lie in two lateral fields be correct then this 

 species is the only exception to the rule that the testes in this genus are 

 irregularly scattered in the field between the lateral vitellaria. The 

 considerations above presented cause one to doubt the accuracy of von 

 Linstow 's statements regarding the number and position of the testes. 

 The vas deferens forms a, thick mass of coils in the middle of the pro- 

 glottid. This mass apparently does not extend over to the cirrus- 

 pouch. In von Linstow 's figure the cirrus-pouch, which he describes 

 as a spindle-shaped muscular organ with a breadth of 0.110 mm., ex- 

 tends just a little within the vitellaria, or about V^-Ys across the pro- 

 glottid. The cirrus (Fig. 169) in the 46.4 mm. specimen was visible at 

 a point 13.8 mm. posterior to the head. It is short and club-shaped, 0.34 

 mm. long, and it extends 0.2 mm. beyond the proglottid 's margin. 



A comparison of cirrus-pouches in Von Linstow 's figures (repro- 

 duced Figs. 167 and 169) shows some evident discrepancies. The cirrus- 

 pouch in Figure 167 is set far within the tissues of the proglottid and it 

 is connected with the exterior by a slender tube. Figure 169 shows by 

 far the more typical condition and is to be considered as the normal 

 for this species. 



The bilobed ovary lies in the posterior part of the proglottid. The 

 lobes are club-shaped. The vitellaria lie in the lateral fields. They dis- 

 charge the yolk-cells through the paired vitelline ducts which pass to 



