430 FAUNA HAWAIIENSIS 



the posterior end, the whole body is hollowed so that each segment is curved. The 

 most posterior segments, which are crowded with embryos well advanced in their 

 development, are rounder, less flattened, longer, and they readily broke off. 



I was not able to detect any genital pore on the exterior even with the aid of 

 powerful lenses, but sections (figs. 4 and 6) and stained mounted specimens show that 

 it is on the same side of the body in all the segments. 



The head of the tapeworm bears four suckers, and in the midst of them is the 

 rostellum (figs. 3, 8 and 9). The shape of the head is very various : in some cases the 

 suckers are, as it were, hunched up and lie at each corner of a square, the lateral 

 diameter of which does not exceed the dorso-ventral (fig. 8) ; in other specimens the 

 head is not separated from the body by a deep constriction, but is flattened and spread 

 out (fig. 7), so that the lateral suckers are separated from one another by a space con- 

 siderably wider than that which lies between the dorsal and the ventral suckers. 



The rostellum is minute and sunk in a pit (fig. 3) ; it bears a wreath of ten hooks. 

 In all the specimens which I cut into sections, and I think in the others as well, the 

 rostellum was retracted, the points of the hooks folded in against the a.xis of the 

 rostellum, and not reaching so far forward as the mouth of the pit. When the animal is 

 fixed to the mucous membrane of its host this rostellum is doubtless protruded from its 

 sheath, and the hooks are divaricated. Certain muscle-fibres which run from the base 

 of the rostellum, and lose themselves in the parenchyma, probably serve to retract it. 



The hooks are slightly curved, and the projection which corresponds with the inner 

 fork of the more triradiate hooks of other genera is hardly, if at all, marked (fig. 2). 

 Measuring in a straight line from the base to the tip the hooks are 18 — 23/^ in 

 length, thus corresponding pretty closely with those of Drepanidotaenia tenuirostris 

 which, according to Railliet', measure 20 to 23 ^a, and to those of D. lanceolata, which 

 measure 25 to 31 /a. 



The four suckers present no peculiarities ; they are deeply cupped, with a small 

 orifice to their lumen, but probably they are capable of considerable change of form 

 (fig. 9). They are probably retracted by some muscle-fibres which cross one another 

 and run into the parenchyma. 



The segmentation of the body begins immediately behind the suckers ; at first the 

 segments are very short, but they gradually increase in size throughout the first three- 

 quarters of the length of the body. For the last quarter the segments are crowded 

 with embryos ; they become in this region much narrower, more cylindrical in shape, 

 and longer, and are very easily broken off. The posterior free edge of the segments of 

 the anterior two-thirds of the body is sharp, and may overlap the segment behind, or 

 may stand out clearly from it. 



The water-vascular system is well developed; on each side of the body are two 

 longitudinal canals, — one, the ventral, much bigger than the other, or dorsal. The 

 ' Traite de Zoologie medicale et agricole, Paris, 1895. 



