BY T. HARVEY JOHNSTON AND O. W. TIEGS. IH 



two well-defined roots. In the other, which is a much more powerful hook, 

 such a basal bifurcation is absent. The disc is provided with two pairs of 

 groups of unicellular glands, the lateral pairs (Fl. xiii., fig. 25) being especially 

 well-defined and appearing to open, by numerous converging ducts, upon the 

 surface of the disc. The two accessory adhesive organs or squamodiscs consist 

 each of about fifteen rows of modified body papillae, and are quite devoid of 

 definite hook apparatus. The disc is well provided with muscles which are 

 modifications of the longitudinal body musculature of the parasite, though it is 

 possible that the circular layer also enters into their formation. The longitudinal 

 muscles of the posterior lateral portion of the worm ai'e arranged on each side 

 in a bundle which passes outwards (PI. xiii., fig. 25) to become inserted on the 

 lai-ge hooks of the corresponding side. From the upper part of the disc near 

 its jimction with the body, there arises on each side a bundle of muscles passing 

 obliquely to the hooks of the other side. The musculature of the sucker-like 

 organs is in the form of a pair of muscles travelling down the ventral mid- 

 line of the body. 



The cuticle is developed into numerous forwardly projecting papillae, eaoh 

 very sharply pointed (PL xiv., fig. 28), but not so closely arranged as in 

 Lepid'Otes. They are especially well developed near the disc, but gradually 

 diminish and disappear towards the anterior half of the animal. The longi- 

 tudinal layer of body-muscles is fairly distinct, but cannot be said to be strongly 

 developed. The fibres of the outer layer ran mostly in an irregular oblique 

 manner; only in places could distinct circular muscles be detected. In the region 

 of the genital openings the musculature undergoes a pronounced modification, a 

 powerful group of irregularly arranged oblique, circular and longitudinal fibres 

 being foimd, surrounding the huge genital cavity to be described below. Into 

 this mass are also inserted well-defined columns of dorso-ventral fibres. The 

 mouth is a transverse slit opening on the ventral surface, a little in front of 

 the region of the brain. The buccal cavity is short, the pharynx large and dis- 

 tinct, and the oesophagus short. Into the posterior part of the pharynx opens 

 a group of unicellular glands, clearly visible in the living animal, but in stained 

 preparations appearing only as a dark mass. The intestine is bifurcated and 

 devoid of caeca. In section its wall is seen to be composed of a layer consisting 

 of several clear hyaline cells. There is no junction of limbs posteriorly. 



Three pairs of head-organs are present, their ducts originating from masses 

 of gland-cells which cause a slight projection on each side of the head. The 

 brain, which lies immediately anterior to and above the pharynx, gives off 

 three pairs of nerves ; a small pair to the anterior extremity ; the second, slightly 

 larger, pair laterally to supply the sides of the anterior half of the body; the 

 third pair very large and passing right along the animal, lying in close contact 

 with the intestine (PI. xiv., fig. 27). 



The excretory system is clearly visible in living specimens as an irregular 

 tube running close to the intestine and receiving branching vessels in the region 

 of the testis. Posteriorly the limbs communicate close in front of the termination 

 of the intestinal branches. The system opens on either side at about a third 

 of the body-length from the anterior end by a pair of dilated excretory vesicles, 

 riowing into the base of this vesicle are the excretory vessels of the head, which 

 in the region of the brain have a curiously complicated course (PL xiv., fig. 27). 



The ovary lies transversely in the mid-region of the body, the oviduct leaving 

 it on its left side to pass inward and then anteriorly where the vagina opens 

 into it. It then passes forward, sweeping round as the uterus past the male 



