168 TAPEWORMS OF HARES AND RABBITS STILES. VOL.XIX. 



60 to 95, but in no case was the strobila complete, as all of them had 

 evidently shed proglottids. In some cases the head was retracted into 

 the anterior segments, as is described for Drepanidotcenia lanceolata. 

 In only one specimen (Plate X, fig. 13) was it extended. The first 

 segment could not be satisfactorily measured; the second segment 

 (No. 1176, U.S.N.M.) measured 0.448 mm. broad (slightly narrower than 

 the head) by 64 /* long, and showed no trace of genital organs. The 

 cirrus was distinctly visible in one specimen in the sixth segment, but 

 no positive statement can be made for the earlier proglottids. In some 

 of the other specimens the cirrus did not appear until several segments 

 later in the eleventh in one case. The poor condition of the material 

 must, however, betaken into consideration in this connection. 



Several segments after the appearance of the cirrus, a roundish body 

 about 16 JJL in diameter appears in each proglottid, alternating a very 

 short distance to the right and left of the median line. This body, 

 which develops first from the eighth to the fourteenth segment, evi- 

 dently represents the receptaculum seininis. In each succeeding seg- 

 ment it is slightly farther from the median line than in the segment 

 immediately preceding, so that we may conclude that the median line 

 of the cestrode strobila is the seat of very active growth, a conclusion 

 supported by observations on other species also, more particularly on 

 the early genital anlageu of Thysanosoma giardi. 1 The testicles soon 

 appear and extend in an irregular line across the median field of the 

 segment, for the greater part distally of the female anlagen; their num- 

 ber could not be ascertained exactly because of the poor condition of 

 the material, but, as nearly as could be estimated from various portions 

 of segments which were in better condition, there are about 50 testicles 

 to each proglottid. 



The genital pores are alternate and situated in about the middle of 

 the lateral margin ; the genital cloaca is generally quite deep. The 

 cirrus and cirrus pouch are quite characteristic and allow an immediate 

 determination of the form. The cirrus pouch assumes various shapes 

 and proportions according to its contraction, but in general may be 

 described as pyriform; it measures about 0.4 mm. long by 0.16 mm. 

 broad; its proximal portion (0.192 to 0.224 mm.) is extremely muscular, 

 being provided with an inner circular layer and an outer longitudinal 

 layer, the two together, in some cases, measuring 16 // thick. The cirrus 

 extrudes from the pouch in the majority of the segments ; when retracted, 

 it appears spinous (wrinkles of the cuticle?) but extruded it is evidently 

 smooth; the largest cirrus observed was 0.24 mm. long by 32 /n thick. 

 The continuation of the cirrus canal in the proximal portion of the pouch 

 is swollen into a vesicula seminalis and from the proximal extremity of 

 the pouch the rather prominent vas deferens extends, somewhat sin- 

 uously, through the anterior portion of the pore side of the segment to 



1 A Revision of the adult cestodes of Cattle, Sheep, and allied animals; Bull. 4 

 Bureau of Animal Industry, p. 63, pi. xn, tig. 3. 



