and W. M. Tattersall. Various results of my study have 

 been published in several (6) papers, among which those 

 being Nos. 3o and 42 of this Bulletin (1905) and the 

 «Siboga» report (1910). 



The really broad foundation of our knowledge of this 

 order was laid by G. O. Sars in his «Challenger» work. 

 It ought to be said that in spite of a number of imperfec- 

 tions or errors in matters of detail it ranks very high 

 by the enormous quantity of observations based on a 

 comparatively large and varied material and set forth by 

 the author in his lucid text and very large number of gene- 

 rally good figures. Sars described 28 species (almost all 

 new), but 3 have been cancelled later, so that 25 remained; 

 5 valid species from the North Atlantic and the Arctic 

 Ocean and 1 species from the Sea of Ochotsk had been 

 established by earlier authors and were not described in the 

 ((Challenger» work. The result is that at the end of 1 885 

 3 1 species now recognized as valid were known. During 

 the next 25 years (1886-1910) several authors have added 

 in all 3o valid species (4. established by Caiman, Holmes, 

 Il lî g and Stebbing, 3 by Holt and Tattersall, 6 by Ortmanri 

 and 17 by myself). And here I give preliminary diagnoses 

 of 12 new species, so that the total number now known 

 of this order is j3 species. 



For various reasons I am apt to think that comparatively 

 few, probably not a dozen, species in the oceans of the 

 globe are still undiscovered. Excepting the South Pacific, 

 from which my material is somewhat scanty, I have 

 examined large or even very rich collections from every 

 large area of the oceans, and no single expedition or 

 Museum contained more than at most two species not 

 found by me in at least one collection from another 

 source. Furthermore the animals are easily captured by 

 tow-nets or vertical nets, and such instruments have been 

 much used by most exploring expeditions since the ((Chal- 

 lenger». And the majority of species have a very wide 

 geographical distribution. It is of importance that I have 



