D.— ZOOLOGY. 85 



monographs would be, I assume, that they should be intelligible to, and 

 render possible the determination of species by, any properly trained 

 zoologist, even without previous experience in dealing with the particular 

 groups of which they treat. 



The Zoological Department of the British Museum may fairly claim to 

 have done more towards this re-editing of the Systema Naturae than any 

 other institution in the world. The long series of monographs, of which 

 the true character is somewhat concealed under the official title of 

 ' catalogues,' is a monument to the learning and industry of the great 

 zoologists who planned and executed them. Though they remain indis- 

 pensable to all serious students of the difierent groups, however, they are 

 now, for the most part, long out of date, and, vast as is their scope, they 

 cover only a fraction of the animal kingdom. 



In 1896 the German Zoological Society began the publication of ' Das 

 Tierreich,' afterwards continued by the Prussian Academy, which was 

 planned to give nothing less than a revision of all the species of living 

 animals. Here again, however, after thirty-four years, only a small part 

 of the ground has been covered and already the progress of research has 

 rendered many of the earlier parts obsolete. Col. Stephenson tells me that 

 Michaelsen's revision of the Oligochseta, published in this series in 1900, 

 deals with exactly half the number of species enumerated by the same 

 authority in 1928. 



Apart from these attempts at comprehensive revision we have, of 

 course, numerous surveys of local faunas on a larger or smaller scale, 

 besides monographs of restricted groups, but hardly ever do these fit 

 together without leaving gaps, geographical or systematic. 



Take, as an example, the Brachyurous Crustacea or true Crabs. No 

 revision of the Brachyura as a whole has been attempted since Henri 

 Milne-Edwards' ' Histoire Naturelle des Crustaces,' published nearly a 

 century ago. The student who wishes to identify a collection of crabs has 

 to begin with local faunas, such as Alcock's invaluable ' Materials for a 

 Carcinological Fauna of India,' and Miss Rathbun's monographs of the 

 American species ; but for regions that have not been thus studied there is 

 no way but to search out and compare the descriptions of species in innumer- 

 able obscure publications by writers who had often an imperfect knowledge 

 of what had been done elsewhere. The genus Pilumnus is one that is 

 abundantly represented in all the warmer seas of the globe. No revision 

 of its numerous species has been attempted in recent times. I do not even 

 know how the genus is to be defined from neighbouring genera ; and yet 

 hardly any report on a collection of tropical crabs does not profess to 

 describe at least one new species of the genus. 



Another example from a very different group of animals is given by 

 the aberrant Lamellibranch Mollusca forming the family Teredinidse, 

 commonly known as ' shipworms.' During the past ten years a great deal 

 of attention has been given to these animals in the effort to discover means 

 of combating or avoiding their attacks on the timber of harbour works 

 and the like. Nevertheless, the taxonomy of the group remains in a state 

 of the utmost confusion. There is no agreement as to the limits even of 

 the genera, and the inconstancy of the characters that have been used for the 

 definition of species is plain to anyone who studies a large collection. 



