MICHIGAN ACADEMY OF SCIENCE. 13 



Nervous system. In the proglottids a single pair of lateral nerve trunks 

 were found. No study of the nerves in head and neck could be made. 



Excretory system. The main excretory vessels of the proglottids alone 

 have been worked out. There are two pairs of main lateral excretory 

 vessels (PI. 1, fig. 4), dorsal and ventral respectively. Of these the ventral 

 vessels are marked by their large size. Both dorsal, and ventral vessels are 

 more or less sinuous, approaching the condition seen in 0. lonnbergii (Fuhr- 

 mann). In well extended proglottids the excretory vessels are almost 

 straight. Both pairs lie mesad to the lateral nerve trunks and to the vitel- 

 laria. A commissure connects the ventral vessels in the posterior part of 

 the proglottid, but the presence of a dorsal commissure could not be ascer- 

 tained. There may be (PI. 1, fig. 4) a more or less intricate plexus of smaller 

 vessels in the posterior regions of the proglottids. The presence of secon- 

 dary excretory openings, foramina secundaria, could not be determined 

 even in transverse or frontal sections. In most of the proteocephalid species 

 examined for this character these openings are readily found. 



Sexual organs. The earliest traces of sexual organs (in 'in toto' mounts) 

 appear as darkly staining lines of cells in the median logitudinal region 

 about 6 mm. from the tip of the head. The proglottids measure about 0.11 

 mm. long by 0.54 mm. broad. Riggenbach (1896) has described the de- 

 velopment of the organs. The adult sexual organs are arranged as usual in 

 species of the group. 



Genital pore. The genital pore is marginal, irregularly alternating, fre- 

 quently with several successive pores on the same side. There is no genital 

 papilla, nor is the pore situated in a depression. In nearly mature, in quad- 

 rate or sub-quadrate and in elongated ripe proglottids small variations may 

 be found in the position of the genital pore. In a few cases the pore was 

 located at the end of the first fourth of the proglottid's length but in no case 

 was it found posterior to this point. It was sometimes found as far for- 

 ward as the end of the first ninth, eighth or sixth. Among long ripe pro- 

 glottids it occurred most frequently at the end of the first sixth. In this 

 extreme forward position of the genital pore this species agrees with the 

 other North American species of Ophiotacnia infesting amphibians. John- 

 ston (1912) found a species of Ophiotae7iia in Hyla aurea of New South Wales 

 which he described as 0. hylae in which the genital pore was located at or 

 very near the middle of the margin of the proglottid. His species forms the 

 only known exception to the usual anterior location of the genital pore in 

 the amphibian Ophiotacnia. 



Male organs. The muscular cirrus-pouch (PI. 1, fig. 3) is pyri-form, the 

 inner end usually somewhat broader than the outer. The position of the 

 pouch is usually at right angles to the margin of the segment but sometimes 

 its inner end is bent posteriad. Measurements of cirrus-pouches from dif- 

 ferent regions of the strobila show that there is some variation in the size 

 of this organ. In nearly mature proglottids two cirrus-pouches measure 

 0.29 by 0.084 mm. and 0.333 h\ 0.092 mm. respectively. In six ripe pro- 

 glottids, the cirri being unprotruded, the cirrus-pouches measure 0.33 by 

 0.116, 0.33 by 0.116, 0.32 by 0.116, 0.4 by 0.133, 0.3 by 0.133, 0.333 by 

 0.133 mm., average dimensions 0.335 by 0.124 mm. These measurements of 

 length are taken from the inner end of the pouch to the margin of the pro- 

 glottid. These cirrus-pouches reach 1/6-1/4 across the proglottid's breadth. 

 Seven cirrus-pouches selected because of protruded cirri were measured. In 

 each of these cases the proglottid to which the cirrus-pouch lu^longed was 

 ripe. Casual examination of these pouches before measurement showed 



