94 J. MURRAY 



related species only occur in tliu groups which lay spiny eggs, or at least the eggs 

 are only of value in that group. 



Now the eggs do not show the characteristic processes while they are in the body 

 of the parent, and once they have been deposited there is nothing to indicate 

 their relation to one animal or another. The actual act of deposition can rarely be 

 observed. 



While the eggs are still soft and their shape readily distorted by the 

 pressure of the enclosing membrane, and of adjacent eggs, the processes are often 

 already formed, and if the membrane be ruptured, the external pressure being 

 removed, the turgidity of the egg causes it to assume its proper shape, and the 

 processes then stand out. The opportunities for completing an identification in this 

 way must be casual and uncertain, and it is oftener possible to find an egg in which 

 the young is so well grown that it shows the distinctive characters of the adult. 



While many species are only distinguishable by their eggs, the converse occurs. 

 Quite distinct species have eggs exactly similar, or so nearly alike that identification 

 cannot be certain. 



These facts show the necessity there is for making an exhaustive study of each 

 species whenever the opportunity offers, and the danger there is that species will be 

 multiplied to no good purpose, if such study is neglected. 



Bibliography. Throughout the text references to the bibliographical list are 

 made in heavy type enclosed in brackets. 



Tables of Species. In the lists of species given to illustrate distribution there 

 was some difficulty in presenting the facts concisely. To classify the records of 

 Tardigrada broadly the world was divided into nine great regions, one for each of 

 the five continents, for Australasia, and for the Antarctic and Arctic Regions. As 

 regards these eight divisions the classification is obvious and natural enough. The 

 ninth division (Oceanic Islands) was introduced to receive a lot of scattered records, 

 not otherwise provided for. This is not satisfactory, as the islands are so scattered. 

 Those which lie near continents are included with them, the others are all slumped 

 together. It is a makeshift which may serve for the moment. Greater accuracy is 

 not called for till a more comprehensive survey of the distribution of all the Tardi- 

 grada is attempted. 



I have given all the records I could find, but many may have been overlooked. 

 Some discrepancies may be found between the number of species for any one region 

 given in different tables. This is due to the fact that many records were added from 

 time to time after the tables were first compiled, and it could hardly be hoped that 

 no errors would occur in collating so many tables. 



In dealing with each country the local distribution is treated with more detail, 

 and in addition to the nine main divisions of the earth's surface there may be given a 

 column for such adjacent regions as may be supposed likely to show some relation- 

 ship. Thus with the Antarctic a sub-Antarctic area is distinguished. 



