438 FAUNA HAVVAIIENSIS 



extrusion of the introvert is believed to be effected by fluid being forced into its lacunae 

 by the lemnisci. It is retracted by special muscles attached to the inside of its tip; 

 besides these, other retractor muscles run from the outside of the introvert sheath, and 

 these serve to retract the whole sheath and its contents into the trunk. The chief nerve 

 ganglion lies as a rule on the posterior end of the introvert sheath, usually in the middle 

 line, but in the Gigantorhynchidae it is placed to one side. From the posterior end of 

 the introvert sheath, and having its origin between its two walls when they are present, 

 the ligament runs backward, traversing the body cavity, and ending in the funnel-shaped 

 internal opening of the oviduct in the female and in the vas deferens in the male. 



Owiny to the absence of an introvert and its sheath, the relations of the ligament 

 in the present species is somewhat altered. It takes its origin from the anterior end of 

 the head, and at first seems to consist of a few strands of muscular fibres which arise 

 from the muscles of the skin (fig. 21). All my specimens but one proved to be mature 

 females, whose ovaries had broken up into the egg masses which are characteristic of 

 the Acanthocephala. These egg masses consist of packets of a dozen or more cells of 

 which the peripheral layer develop into ova at the cost of the central cells which serve 

 them as a food supply (figs. 14, 16, and 23). These packets coexisted in my specimens 

 with ova in various stages of development, some without any &^^ shell, whilst others 

 were provided with a thick deeply-staining membrane. The whole lumen of the head 

 was crowded with these ova. In the region of the collar the ova were confined by a 

 thin-walled membrane, and in the trunk there were two such masses of ova, which, 

 however, seemed less mature than those lying in the head. Lying amongst the 

 various organs in the body-cavity were a number of very finely granular masses, which 

 I take to be the masses of spermatozoa (figs. 16 and 20). Of the complex system 

 by means of which the ova leave the body, little could be made out beyond the fact 

 that a well-marked funnel is present opening into the posterior end of the body- 

 cavity of the trunk (fig. 19). I failed, however, to find a second opening near the 

 narrow end of the funnel such as occurs in other forms, but this may have been 

 due to the poor state of preservation. The funnel leads into a duct which opens on 

 the posterior end of the trunk. 



The testes are two in number, and lie one behind the other in the ligament, 

 though owing to its looping both may appear in the same transverse section. The 

 spermatozoa do not escape into the body of the male as the ova do into that of 

 the female, but pass down a duct in the ligament which opens at the end of the 

 body. Traces of accessory glands were seen, but the details were not clear. 



The brain lies on or in the ligament just behind its point of attachment to the 

 skin of the head (figs. 2 i and 23). Owing to the disruption of the ov'aries in my female 

 specimens the ligament could not be traced very far, but in the only male it reached 

 from one end of the body to the other. The brain consists of a few large ganglion 

 cells with a clear homogeneous cytoplasm and deeply-stained nuclei ; the divisions 



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