A NEW SPECIES OF AVIAN TAPE-WORM. 157 



which the genitalia were but rudimentary. Thus, although 

 Krabbe gives no length, Pagenstee her's worm, I compute, could 

 not have been more than 2 mm. in length ; and Krabbe's 

 2-mm. w^orm was, I am led to deduce from the rudimentary 

 condition of the genitalia, but a young specimen of his larger or 

 30-mm. worm with 500 segments. 



In comparison with my worm, whose greatest length is 3*712 

 mm., and breadth 0*245 mm., consisting of twenty-five segments, 

 the strobila and the segments are greatly out of proportion 

 in length and breadth compared with Krabbe's 2-mm. speci- 

 men. In the case of Pagenstecher's specimen I am inclined 

 to the opinion that his worm is identical with mine ; for if four 

 segments were added to a worm which contained unripe ova, and 

 assuming that each of these segments w^as, as in the twenty- 

 fi^fth segment of my worm, 0*371 mm. long, Pagenstecher's worm 

 would then read thus : 21 segments = 2 mm. + 4 segments x 

 0*371 mm. = 1*484 mm. -f- 2 mm. = 3*484 mm., the equation of my 

 specimen, less 228 mm. They would thus have been elongated 

 to 3*484 mm., and would undoubtedly have developed into mature 

 or ripe segments in the strobila with the jDeculiarly formed egg- 

 masses which he found amongst the faecal substance in the duck. 

 Considering that Creplin's worm unicrosoma is supposed to have 

 been inerme, the omission by Krabbe in his drawings of the 

 cephalic hooks of Pagenstecher's specimen, in comparison with 

 his own, is regrettable ; they would have been invaluable, for 

 then we should have had a surer and broader basis for the- 

 determination of this species, as the term microsoma, as I have 

 said above, is vague, and might with propriety be applied to other 

 species of avian tape-worms. Krabbe does not appear to have 

 convinced himself from an inspection and comparison of the hooks 

 of his 2-mm. worm with the hooks of Pagenstecher's specimen 

 that these two worms were identical. To compare this species 

 of avian tape-worm, microsoma, with its narrow attenuated seg- 

 ments, with that of mine, the breadth of whose terminal segment 

 is two-thirds its length may well seem anomalous, the gradation. 

 of the last seven segments in the evolution of the genitalia being 

 definitively marked, and only one segment in the strobila a 

 perfect hermaphrodite segment. Then again, although the 

 cephalic hooks in my specimen. Fig. 4e, are a trifle shorter 

 than Krabbe's 2-mm. specimen, Fig. 4(Z, yet otherwise they 



