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



of the excellent observers who did the pioneer work among the 

 Rotifers and Infusoria appears to have seen them before Pastor 

 Goeze in 1773 (9), and that for more than half a century 

 afterwards (till 1840) they were considered to be rare, most 

 naturalists who took any notice of them supposing that there 

 was only one kind. 



In 1840 Doyere's fine memoir (2) appeared, in which Tardi- 

 grada were first accurately described and figured, and our 

 knowledge of their organisation greatly extended. 



The great advance made by Doyere over all previous observers 

 might have been expected to give an impulse to the study of the 

 Tardigrada, but this was not so. Activity continued to be 

 spasmodic, and works which marked any advance in knowledge 

 of the group appeared at intervals of something like twenty 

 years. It is only necessary to mention GreefT's careful studies 

 (1865-6) (10, 11) and Plate's monograph (1885) (25). 



Plate offers a convenient opportunity for recapitulating 

 what was known of Tardigrada up to that time. He admits 

 six genera and twenty-five species. One of the genera and 

 several of the species cannot be admitted as valid, being 

 either larval states or peculiar (perhaps pathological) conditions 

 of other species. Moreover, Plate's own new species are very 

 inadequately described, compared with Doyere's. On the whole, 

 Plate advanced the knowledge of species but slightly, though 

 his contribution to the knowledge of structure is most valuable. 



The only other work calling for remark appearing before 

 the close of the nineteenth century was Scourfield's notes on the 

 Tardigrada of Spitzbergen (1897) (44). Unfortunately, Mr. 

 Scourfield limited his work on the Tardigrada to this one effort, 

 and it is matter for regret that he did not turn his attention 

 to the Tardigrada of our own country. 



With the year 1900 Richters (27-37) appeared in the field, 

 giving a fresh impulse to the study, and first recognising that 

 Water-bears are really pretty numerous. The first of my own 

 papers on the subject (15-22) appeared in 1905. 



In the following notes on the Tardigrada I have tried to give 

 as much information as will enable the beginner to recognise 

 a Water-bear when found, and to discriminate between different 



