172 J. MURRAY 



straight for somewhat more than half their length from the points. They are then 

 enlarged and curved outwards to the furca. The pharynx is a little longer than 

 broad. The end of the gullet bears the apophyses. The nut next the gullet is 

 scarcely longer than broad ; the second is a little longer, and the third a little longer 

 still. The first is nearest the middle line, and the second and third diverge successively 

 farther from it. 



The stomach is oblong and very slightly coloured. Its separate cells are not 

 conspicuous. 



One egg measured 70 M by 36 M, but others were rather shorter. The newly 

 hatched young was 100 /u. in length. 



There are few species with which it is necessary to compare M. canadensis very 

 carefully. The Macrobioti which lay smooth eggs are not so numerous as those which 

 lay rough eggs. There are two principal groups of them, one comprising species 

 which have warts or spines or distinct papillae on the body, the other species which 

 are smooth or very finely papillose. In the former group there are several which 

 have three short nuts in the pharynx ; in the second group, to which M. canadensis 

 belongs, there are only two which have the pharynx of this type. 



M. tetradactyloides, Richters (35), and M. schaudinni, Richters,* are very similar 

 to M. canadensis. Both are, however, much larger and more robust animals. 

 Richters himself considers the size important in distinguishing M. tetradactyloides 

 from M. tetradactylus. M. schaudinni is nearly twice as long as M. canadensis, and 

 M. tetradactyloides is larger still. It is pretty certain that M. canadensis is really a 

 small animal, although some water-bears vary greatly in size. It was very common 

 in some parts of Canada, and yet it was uniformly small. The largest measured was 

 only 225 n in length, and many mature- looking animals, with eggs in the body, were 

 less than 200 M. 



M. canadensis may be distinguished from M. tetradactyloides by the unequal 

 pairs of claws and by the greater inequality of the claws of each pair. It is more 

 difficult to separate from M. schaudinni, which has the pairs unequal. Richters 

 figures his species with much robuster claws. 



In M. canadensis the claws are intermediate between the Diphascon type and the 

 V type. The long claw of each pair is very slender, and that of the larger pair is 

 almost bristle-like, as in M. oberhauseri. The bristle-like claw is set on to the lesser 

 claw of the same pair in the same manner as in Diphascon, but nearer to the base. 

 The two claws diverge very widely. 



While usually smooth, it sometimes happens that the body is finely papillose on 

 the posterior half, or more than half, though never all over. 



The nuts of the pharynx are only slightly rounded at the ends, not enough to 

 destroy their quadrate character. 



Habitat. Victoria, British Columbia, and the Rocky Mountains, abundant. 

 * " Tardigraden-Studien," Ber. Senckbg. Nnturf. Ges., 1909, p. 32. 



