THE TAPEWORMS (CESTODA) OF THE RED GROUSE 341 



(ii.) Davainea cesticillus (Molin), 1858. 

 Synonym : TiBnia cesticillus (Molin). 



This is a small species; the majority of our specimens measured between 5 '5 

 and 9 mm. in length. Few were longer, though many were shorter. They were 

 all young immature specimens. The broadest at the broadest part, usually about the 

 level of the last proglottis but two or three, measured 1 mm. across. They 

 tapered to the last proglottis, which averaged about 0'5 mm. in diameter, and 

 still more do they taper towards the head, where the narrow neck is but 0'2 mm. 

 The head itself is 0"3 to 0*5 mm. across, and perhaps two-thirds of this in length. 



The hooks in the rostellum were numerous, I should judge a few hundred, 

 but I could not, on account of their minute size, count accurately : they measured 

 about 7(" in length. 



The head when the rostellum is withdrawn is somewhat cup-shaped, and the 

 four suckers are on the edge of the cup, opening at the edge and slightly inwards. 

 There is practically no " neck," just a constriction between the head and the first 

 proglottis. Behind the head the proglottides increase markedly in size, and the 

 third proglottis in most specimens is already as broad as the head. Tliey are 

 deeply imbricated, and the overlapping edge is full and rounded. At the level of 

 the anterior end of each proglottis is a constriction which slightly separates off the 

 overlapping lobe from the preceding proglottis, to which it, of course, belongs. 

 This gives a somewhat ear-like outline to the side of each segment. The constriction 

 first appears in about the tenth proglottis, and the characteristic outline is lost in 

 the last, where the overlapping edges curve in as if to guard the excretory opening. 

 The total number of the proglottides varies a little with the variable length, but 

 differences in length depended far more on the state of contraction of the body 

 than on the number of segments. Roughly speaking, the numbers varied from 

 about eighteen to about twenty-eight proglottides. 



The genital pore is alternate, and fairly regularly so ; the penis often projects, 

 and then it is apparent that the pore lies rather anteriorly, and is all but over- 

 lapped by the imbricated edges of the proglottis next in front. 



Sections show that there are a number of calcareous bodies in the tissues ; 

 some of these are in optical section brick-shaped, and others spherical or shaped 

 like a cottage-loaf. These latter are bigger than the others, and show numerous 

 radiating lines. Posteriorly the tissue becomes very highly vacuolated, and the 



