J. MURRAY ON WATER-BEARS, OR TARDIGRADA. 185 



down some of these distinctions, and the new genera established 

 in recent years go further in the same direction. 



Echiniscus and Macrohiotus remain distinct ; the differences have 

 not all broken down, but they do not stand so far apart as was 

 at first supposed. All Echinisci are still armoured, and Macrohioti 

 unarmoured. All Echinisci have still some processes on the head 

 (if only the seta a), all Macrohioti have none, unless the papillae 

 on the head of M. ornatus and M. jxtpillifer be regarded as homolo- 

 gous with a. All Echinisci have disunited claws, similar except 

 fov the " barbs," when present ; all Macrohioti have the claws 

 united in pairs. The other distinctions are not now confined to 

 the respective genera. 



Chitinoiisrods in 'pharynx. All Maa^ohioti normally have these, 

 Echinisci usually lack them. Some years ago Richters (36) noted 

 rods in E. islandicus. Any Macrohiotus may be found without 

 the rods, but that is only a temporary condition, the " simplex," 

 connected with the moult. No other genus has the rods, except 

 Diphascon, and tliat is very close to Macrohiotus. 



Tooth-hearers. Six out of the ten known genera are described 

 as having bearers ; no species of Echiniscus is said to have them. 

 Quite recently, however, Herr Thulin, of Lund, Sweden, has sent 

 me drawings of a true Echiniscus which has bearers. The species 

 is a somewhat aberrant one and agrees very closely with one 

 which I myself described recently, E. intermedius (25), so closely 

 that, till we have further information on the subject, I must 

 assume that I overlooked this very important character. 

 Making yet another link between Ec/ii7iiscus and Macrohiotus^ 

 Oreella has pharynx, teeth, gullet and bearers precisely like those 

 which Herr Thulin has drawn for the animal which I identify 

 as E. intermedius. Halechiniscus has " bearers," thus linking 

 Echiniscus with Oreella bv another route. 



Setae and jmljjs on the head. A typical Echiniscits has ten 

 processes on the head ; near the mouth two pairs of cirri and 

 a pair of blunt palps ; at the base of the head a pair of 

 lateral cirri; and at the base of each a small blunt palp. 

 With minor modifications in proportions, these are present in all 

 known species, except E. cornutus Richters (37) and E. imherhis 

 Eichters (42). In E. cornutus seta a is modified into a thick 

 curved spine, like a cow's horn; the anterior cirri near the 

 mouth are replaced by little knobs and the posterior pair by 



