T. B. ROSSETER ON THE ANATOMY OF DICEANOTjENIA CORONULA. 365 



the pouch the vesicula seminalis " inferior " ; because the latter 

 is merely for the storage of the sperm previous to its reception, 

 by the medium of the cirrus, into the receptaculum seminis ; 

 whereas the functions of the former are of a more important 

 nature, viz., the development and perfecting of the spermatozoa. 



It is not my intention at this stage to describe the growth and 

 evolution of the genital tract, but merely to remark that in 

 its early stage of development the male genital organ is a long 

 sinuous tubular body, whose orifice is formed like the distal end 

 of a speaking-trumpet, or the corolla of the Caprifoliacese (Fig. 9). 

 This sinuous tube afterwards forms the vas-deferens inferior. 

 In mature specimens the orifice is raised within the cloaca, or 

 it is surrounded by a coating of ring muscles, and an outer 

 layer of undulating longitudinal muscles, intermingled with 

 cellular tissue. It assumes, by contractility, various forms, such 

 as circular, quadrangular, and stellate or pentagonal ; its normal 

 diameter is 0"034: mm. 



The cirrus-pouch ( Fig. 5 a /) is a complex muscular structure ; it 

 is situated in the anterior dorsal proximal third of the proglottis, 

 but it is ventral to the dorsal nerve. It is an elongated 

 pyriform body, whose length is approximately 0"354 mm. and 

 width through the median line 0'135 mm. It is composed of 

 a structureless cuticle ; a layer of broad obhque muscles 

 having, individually, a diameter of 0*007 mm. ; a middle layer 

 of very fine thread-like closely compacted circular muscles ; 

 and lastly there is a layer of longitudinal muscles (Fig. 10). In 

 oblique sections, likewise in transverse sections, through the 

 proximal portion of the pouch, these longitudinal muscles are 

 seen to be seventeen in number, having a diameter of 0'003 mm. 

 These muscles are enclosed by the endothelial wall, which is an 

 inversion of the ectoderm ; it also forms the cirrus sheath, which 

 attaches itself to the vas deferens at the base of the cirrus. 



The cirrus (Figs. 5 A and 11 A) is a long cylindrical flexible 

 organ; its deferent pore is strengthened by a band of circular 

 muscles; its length is 0*05 — 0*07 mm., and diameter 0'0I3 mm. 

 It is not spinous, as Dujardin states it to be, but is a perfectly 

 smooth tube both exteriorly and interiorly ; and, together with 

 its sheath, is invaginated within the pouch. The cirrus-sheath 

 {Figs. 5 A, 12 and 13 i), is interiorly thickly covered by minute 

 opines; they are not "wrinkles of the cuticle," as, when the sheath 



