168 J. MURRAY 



united to it as a variety. Subsequent experience of the animal in many parts of the 

 world established confidence in the constancy of its peculiarities. The absence of a 

 " comma " in the pharynx cannot be considered an important specific character, but 

 when we find it constantly associated with an areolated egg, while M. echinogenitus 

 has a conspicuous comma, and non-areolated egg, the character adds weight to the 

 other specific distinctions. 



Habitat. Among moss, Kooky Mountains, British Columbia, and Ottawa, 

 June 1909. Widely distributed over the world recorded from Spitsbergen, Scotland, 

 India, Tropical and South Africa, Australia, New Zealand, &c. Richters (39) has 

 recorded it from Ascension and Comoro. 



Arctic examples have attained to a larger size, but the Canadian eggs are the 

 largest yet seen. 



The rods in the pharynx are relatively shorter and broader in the young 

 (Fig. 53 is drawn from a young hyaline example). In the adult they are linear and 

 curved. 



The characters of the egg sufficiently distinguish the species from all others 

 hitherto described. There are some species, not yet described, which have the 

 surface areolate in the same manner, but the processes of different form. 



If the egg is not found, the identification is less certain. The presence of three 

 equal linear rods, without a comma, and of divergent claws, united at the base only, 

 differentiates it from the typical forms of hufelandii, harmsworthi, and other related 

 species. According to Richters, however, M. hufelandii may have three equal rods, 

 and the claws may be joined at the base only. The other species probably vary in 

 the same manner. 



Since Richters' original diagnosis of M. echinogenitus was evidently too compre- 

 hensive, and included several forms which we are now, after extended experience, 

 enabled to separate, it will be well to take a review here of the group of related 

 species. 



Richters, in his description, recognised two forms which he distinguished as a 

 and b, but he did not bestow separate names on them ; a has three " bacilla " and a 

 " comma " in the pharynx, l> has two equal bacilla, and a comma. Both have 

 V-shaped claws and the eggs are exactly similar in form, but that of a is much 

 larger. 



M. harmsworthi was at first separated from echinogenitus on account of the form 

 of the claws alone, which were joined for about half of their length, as in M. hufe- 

 landi. Richters considers that the claws vary in the amount of union, just as those 

 of hufelandi do, but assents to the separation of M. harmsworthi, which he supposes 

 to be his echinogenitus a,* on the characters of the pharynx. 



M. areolatus is also supposed by Richters to be included in echinogenitus a, but 



* See Richters' "Tardigraden aus den Karpathen," Zool. Anzeiy., Bd. 3C, July 1910, p. 7. This 

 paper appeared after our Bibliographical List was completed, so could not be included in its proper place. 



