BY T. HAEVET JOHNSTON AND O. W. TIEGS. 103 



of the papillae which eovier the body. The disc is supplied with muscles which 

 originate from a powerful band in the dorsal region of the posterior end of the 

 body, but their detailed arrangement has not been determined. 



On account of the minute size of the worm, the stracture of the body-layers 

 is difficult to observe. The most remarkable characteristic of the epidermis is 

 the presence on it of numerous scaly papillae. Delicate longitudinal muscle- 

 layers lie below this, but their arrangement could not be accurately observed. 

 The body parenchyma is well developed. 



The vei-y small mouth is situated ventralljf immediately in front of the 

 pharynx; the buccal cavity is quite short and the pharynx large, prominent, 

 and projecting upward. Numerous unicellular glands occur in the anterior two- 

 thirds of the wall of the pharynx. No definite oesophagus is present. Im- 

 mediately behind the pharynx lies a mass of glands {? unicellular), which open 

 into the intestine and are especially visible in young specimens. The forked 

 intestine ends blindly at the posterior end of the worm, but immediately before 

 . the termination a junction takes place between the two limbs. In young forms 

 this fusion does not occur. There are no caeca. The intestine is lined by a 

 single row of flattened cells. 



Four pairs of head-organs are present, but no coiTespondiug lobes are 

 developed on the head. Through these structures pass the ducts from a pair of 

 prominent masses of unicellular glands, one on either side, antero-laterally to the 

 pharynx. The excretory system could not be traced satisfactorily. At the an- 

 terior end, immediately behind the mass of gland-cells there occurs, on each 

 side, a duet terminating on the body-surface by a slightly bulbous opening. Into 

 each of these ducts there appears to open a very fine longitudinal duct, while 

 one of a somewhat similar nature can be seen along each side just above the 

 anterior termination of the lateral vitellaria. It is probable that these structures 

 are parts of a complex excretory system (PI. xv., fig. 36). 



The brain lies anterior to the pharynx and gives oft' on each side a pair of 

 nerves to the eyes which consist of a mass of minute pigment cells. The eyes 

 lie close to the brain, i.e. within the "head," being situated, however, nearer the 

 dorsal than the ventral surface. The posterior pair are the larger. 



In this species the male organs reach maturity before the female. In young 

 forms the testis is very large (PI. xvi., fig. 41) occupying a great portion of the 

 body behind the ovary which at this stage is quite immature. In these the vas 

 deferens arises from the outer edge of the testis and leads into a long thin vesicula 

 seminalis which proceeds nearly as far forward as the pharynx, then becoming 

 bent on itself. A bulbus ejaculatorius is present, but is difficult to detect and 

 its connection with the vesicula could not be made out in these young forms. 

 The ciri-us in these is a simple chitinous tube, lying in the cirrus-sac. In close 

 connection with the posterior end of the vesicula are two large glands, probably 

 prostate, which, when viewed in cleared specimens, have a slightly granular 

 appearance, while in transverse section they appear to consist of a number of 

 deeply-staining rings, each arranged concentrically round a nucleated cell. 



In adult forms the testis (PL xvi., fig. 38) is greatly reduced or practically 

 absent , having diminished very much in size, with its cavity practically obliterated 

 and containing merely connective tissue fibres, though a few sperms may oc- 

 casionally be stiU visible. Sometimes (as in the specimen figured) the testis 

 does not degenerate quite so much (PI. xv., fig. 35). The adult vas deferens 

 is much thicker and its opening into the vesicula is pushed forward. The 

 vesicula, which has increased enormously in size, due to the emptying into it 



