12 T. B. ROSSETER OX DREPANIDOT.EXIA YENUSTA. 



gives such a beautiful appearance to the scolex, and which induced 

 me — on the suggestion of Dr. Blanchard of Paris — to give it the 

 specific name " Venusta." On total inversion the rostrum stands 

 lip, " like a candle in a lantern," and there appears on the sloping 

 sides, half-way down the interior of the scolex, an annular forma- 

 tion. The transverse diameter of the scolex, when taken from the 

 mucous membrane of the intestine of the duck, is 0*675 mm. ; 

 and its vertical length 0"405 mm. The length of the rostellum 

 is, in my prepared specimens, 0"405 mm. ; thus the inversion of 

 the rostellum is, approximately, the vertical length of the scolex ; 

 and the depression being formed by the inversion of the rostellum, 

 it follows that 0*405 mm. is the depth of the crater, or hollow 

 of the bowl. 



The Strohila. — The length of the strobila varies according to 

 the age of the Tnenia ; the smallest of my collection of this 

 species measuring | in., and the longest 5 J in. The former was 

 a sexually immature specimen, being composed of 15*2 and the 

 latter of 620 proglottides, and yet this was not a complete worm, 

 it having already shed that portion of its strobila w^hich had 

 become mere uterine egg-sacs. The neck (Fig. IcZ) is very short ; 

 in fact, segmentation commences so close behind the scolex, and 

 the segments are so very incipient, that diflSculty is experienced 

 in accurately defining the exact distance from the scolex in which 

 there are no segments ; its length is not more than 0*200 mm. 

 As the strobila continues its course the segments gradually enlarge 

 both in length and breadth, but there is no perceptible change in 

 their histology until the 218th proglottis is reached ; and here 

 we see the " Anlage," or commencing formation of the male 

 organs — viz., the three testes. They are situated in close proximity 

 to each other, and as yet there is no trace of vasa efferentia 

 between them ; their diameter at this stage is 0*050 mm., and 

 the vertical length of the proglottis 0*090 mm., its width being 

 0*473 mm. On the dorso-anterior side, which is the porose side, 

 near the proximal margin of the 240th proglottis, can be traced the 

 '• Anlage " of the cirrus, with its pouch ; also at the margin the 

 early muscular growth of the genital pa pillar ; and at the 280th 

 segment the cirrus is mature, but the cirrus pouch has not 

 assumed the ampulla form of the future vesicula seminalis 

 superior. The testes, too, have undergone a great change : they 

 are more gloV.ular, have increased their dimension to 0*070, and 



