90 W. BLAXLAND BBNHAM. 



agrees with the rostellum of certain other species of avian 

 Cestodes. 



The rostellum in both the present species consists essen- 

 tially of two concentric muscular sacs, each filled with a fluid 

 (figs. 15, 16). The inner sac is the true rostellum; the outer 

 sac is the " receptaculum rostelli/' the wall of which is 

 reflected on to the rostellum over a certain area, so that the 

 latter may move in and out of the receptaculum. 



The rostellum itself is more or less ovoid, but is divisible 

 into two unequal regions by a circular constriction or neck 

 near the distal end. The smaller of these regions is capable 

 of protrusion, and bears the crown of hooks ; it may there- 

 fore be termed the ^'acanthophore" (figs. 16 et seq., h) ; the 

 proximal region is about twice the size of the acanthophore, 

 and owing to its function may be termed the reservoir (c). 

 The wall of this inner sac or rostellum consists of an outer 

 layer of longitudinal muscle, and below of circular muscle 

 (fig. 21, 1. c). The longitudinal muscles extend up to the 

 level of the insertion of the " guard " of the booklets ; the 

 circular coat is distinguishable beyond this level, and ceases 

 at the distal limit of the ^'handles" of the booklets (fig. 20). 

 This circular coat is much thicker at the neck than elsewhere, 

 and it is due to its presence here that the constriction is 

 so marked (figs. 16, 17). 



The longitudinal coat is difficult to distinguish in flat 

 preparations of the entire object, but in transverse sections 

 is visible enough. 



Just above the neck, but below the booklets, is a series of 

 radial muscles, which in most preparations are seen to be in 

 two layers or strata, one above the other (figs. 16, 19, e). 

 These bundles of muscles arise from the wall of the sac, and 

 there are spots visible below the interspaces between the 

 hooks; consequently there are as many bundles of radial 

 muscles as there are booklets (fig. 17, e). Possibly the 

 duplication of these muscles is in relation to the double 

 circlet of booklets. 



In the reti'acted condition of the rostellum these radial 



