624 Transactions of the Society. 



basket wliicli has been squeezed so as to have a rectangular trans- 

 verse section, or the silk-well of a lady's work-table. There appear 

 to me to be thin rods keeping the membrane stretched, as I have 

 described ; but I have not been able to satisfy myself that they 

 resist the action of caustic potash, and they have not apparently 

 been observed either by Dalrymple, Leydig, or Gosse. Possibly 

 the membrane may be kept stretched by fine muscular threads at 

 the four corners ; but I have not been able to see any. The dorsal 

 view of the apparatus (fig. 12) moreover, shows two strongly 

 marked curved lines — two of my supposed rods — from which the 

 membrane falls inwards towards the centre of the pharynx so that 

 its dorsal wall becomes a kind of cup. This can be readily seen 

 with dark-field illumination, when the line of sight passes through 

 one of the dorsal edges of the pharynx. The appearance so 

 presented seems to require the existence of some stifi" kind of 

 support down the four pharyngeal edges. This strange contriv- 

 ance, which is common to all the species, can be suddenly dilated 

 so as to cause a partial vacuum, and thus engulf the creature's 

 prey ; and that it is very efiective is clear from my finding in the 

 stomach the teeth of a young Asplanchna, an animal nearly half 

 the size of that which devoured it. I have repeatedly seen the 

 larger specimens attack the smaller ones, nibbling at them with 

 their jaws, but without success ; for the smaller Asplanchna drew 

 in its head, and distended its skin to the utmost, so that the jaws of 

 its enemy slipped over the smooth, taut, yet yielding surface ; as 

 unable to penetrate it as a man would be to bite a blown-out 

 bladder. When the Asplanchna falls a prey to its bigger brother, 

 it is doubtless swallowed whole. 



The pharyngeal membrane is produced from the dorsal surface 

 of the pharynx into a long slender and very extensile oesophagus 

 (figs. 13, 14, 9), down which run long ribbon-like muscular threads 

 (fig. 10). Not unfrequently the oesophagus becomes loaded with 

 food for which there is no room in the stomach, and sometimes so 

 much so as to make the stomach look twice its proper size. 



The two gastric glands placed where the oesophagus joins the 

 true stomach are, under dark-field illumination, quite pellucid; 

 except in one bluish- white spot which has a granulated appearance. 

 By transmitted light each is seen as in fig. 11, showing an opening 

 embraced by the end of a winding duct leading to the stomach. 

 The gastric glands have clusters of cells imbedded in them, with about 

 four or five cells in each cluster (fig. 9). The stomach has thick 

 walls studded with clear round cells which (Dalrymple suggests) 

 may secrete the yellow-brown fluid that colours the food after it 

 has been swallowed. 



There is not a trace of intestine or anus : the stomach has but 

 one opening, and is kept in its place^ by two muscular threads, one 



