ASPLANCHNAD^E. 121 



inwards at the ventral surface, to the buccal orifice. This latter opens directly on the 

 jaws, which are two stout hooked rami with their fulcrum plate imbedded in a horse- 

 shoe-shaped cushion : doubtless, as Mr. Gosse suggests, the third lobe of the mastax : 

 there are no other lobes, so the jaws are practically free. The muscular bands which 

 open and shut these formidable nippers are shown in fig. 8e, and can be seen with ease. 

 Immediately below the horseshoe-shaped ring, and partly embraced by it, is a chamber 

 or pharynx formed by a delicate membrane strained over four curved rods, which hang 

 downwards, and are joined together at the bottom by cross pieces. This curious con- 

 trivance resembles somewhat in shape the silk well of a lady's work-table. By suddenly 

 pulling the four rods apart at the top, the animal causes a partial vacuum, and any prey 

 near the buccal orifice is instantly engulfed. I have seen this happen often, even to 

 Rotifera of considerable size ; for A. Ebbesbornii, like all the Asplanchnce, is an indis- 

 criminate feeder, and will swallow even such awkward mouthfuls as Triarthra longiseta 

 and Bracliionus Bakeri ; the latter of which I have seen with its posterior spines 

 actually piercing the stomach and body walls of the Asplanchna, while the former I saw 

 head-downwards in the oesophagus, with its long propellers stretching right up almost to 

 the buccal orifice. From the pharynx, on its ventral side, stretches a very long trans- 

 parent and extensile oesophagus, down which run ribbon-like muscular threads. Not 

 unfrequently it is loaded with food, so that the creature seems then to have a stomach 

 of twice the usual size. The gastric glands (figs. 3c, 3d) have each a large duct lead- 

 ing to the stomach, and the cells imbedded in them lie together in clusters of four and 

 five. The spherical stomach has thick cellular walls with a clear round nucleus in each 

 cell ; it is often divided for a time into two unequal portions by a deep muscular con- 

 striction, as in fig. 3a. There is not a trace of intestine or cloaca : the hind end of the 

 stomach is merely attached to the body by two fine threads. The faecal matter is 

 rejected through the mouth ; it is slowly driven up by successive contractions of the 

 stomach and oesophagus, till it reaches the pharynx, where it is grasped by the jaws and 

 tossed out through the buccal orifice. There is a rectangular nervous ganglion just 

 under the corona, touching the buccal orifice on its dorsal side, and carrying a crimson 

 eye. A nerve-thread passes from each of the four corners to one of the antennae. Two 

 of these latter are on the dorsal side of the body about half-way down, and two others 

 are on the coronal apices. There is yet another pair on the corona just above the 

 buccal orifice, and to these branch nerves are sent from those of the second pair. The 

 ovary is horseshoe-shaped, flattened at the ends, and studded with germs which are 

 often clusters of cells (fig. 3h). The ova are always developed at the hind-surface of 

 the middle of the ovary : and, when they attain some size, they drop off into the ovisac, 

 a funnel-shaped pocket with its broad base attached to the contractile vesicle. The ovi- 

 sac ends in an oviduct, which opens on the ventral surface in a transverse slit. Occa- 

 sionally I have met with specimens that had as many as three or four ephippial eggs 

 in the ovisac at once ; but generally there is only one maturing ovum, or a young 

 animal lying across the parent with its head presented to the opening of the oviduct. 

 The birth of the young is almost instantaneous; and I have seen it expelled with such 

 force that its stomach was driven right through its mouth, so that it was born with its 

 ciliary wreath half-way down its body. The ephippial eggs ' are circular, corrugated, 

 and often tinged yellow ; as is sometimes the ovary itself. 



The male (fig. 3i) is rather more than half the size of the female, and bears two small 

 additional appendages below the neck. As usual, the entire digestive tract is absent. 

 There are, however, some rounded masses adhering to the dorsal surface, just below the 

 hump. Possibly these may be a kind of stored-up material to compensate for the male's 

 inability to take nourishment. 



The sperm-sac with its enclosed spermatozoa, and the penis, are shown in fig. By'. 

 The penis is a tube with delicate longitudinal furrows sheathed in soft granular masses, 



1 Two cpbippial eggs arc shown in fig. 3. 



