l:;s "TERRA NOVA" EXPEDITION. 



but slight Iv depressed, the 1 breadth, which measures about one-half of the length, being 

 al \vavs a little greater than the height. The cyst-walls are thin and luicalcified. The 

 usual openings are present near the extremities, but, unlike the specimen described from 

 i In' ( 'rinoid arm, these are approximately equal in size, having a diameter of about 

 1 millimetre. 



The above description shows that both in structure aud position on the host, the 

 four cysts from Station 355 differ markedly from all previously recorded examples; the 

 worms enclosed in them correspond, however, so closely both with those from the fifth 

 cyst and with those described by v. Graft', v. Stummer-Traunfels, and Met 'leudon, that 

 I have no hesitation in referring them all to the same speeies. 



One of the cysts on the body-disc of Promachocrinus kerguelenensis was left intact, 

 all the others were opened, and each was found to contain the usual pair of Myzostomes, 

 consisting of a large individual (so-called " female") occupying the greater part of the 

 cyst-cavity, and a small individual (so-called " male ") lying in the narrow space 

 between the former and the cyst-wall. 



The large individuals all had the characteristic " tubular " shape, the sides of the 

 body being bent upwards so that the lateral margins come almost to meet in the 

 mid-dorsal line ; the margins were never found overlapping as in some of the specimens 

 described by v. Stummer-Traunfels. In their rolled up condition the measurements of 

 these individuals are as follows: 



d . 



Specimens <i, /> and c are from the cysts on the body-disc of PromacJiocrinus 

 kerguelenensis. It will be noticed that these are slightly depressed in shape, in 

 conformity with the shape of the cysts. The orientation of these large individuals 

 within the cysts was characteristic and evidently constant ; each worm, as usual, lay 

 with its ventral surface downwards, but its vertical plane was not at right angles to 

 the surface of the disc, being inclined slightly to one side, so that the mid-dorsal line, 

 represented by the groove between the body margins, came to be. directed towards the 

 anal tube of the (Jrinoid host. 



1 have not much to add to previous accounts of the structure of the large 

 individuals (<;/'. Figs. 1-3). The parapodia ar3 quite small, almost vestigial ; suckers 

 and cirri are absent. The ventral surface of the body is smooth and not sculptured ; 

 in some specimens it is divided up into a number of areas by faint grooves (Fig. 1). 

 The mouth is situated at the bottom of a deep anterior concavity, the pharynx is 

 protruded through the cyst-opening in the majority of cases, and appears as a. stout 

 cylindrical organ, without papilhe on the oral margin. 



