PROVISIONAL PREFACE. XI 



working naturalists may have them in their hands at the earliest possible 

 date ; and to avoid as far as possible the multiplication of synonyms by the 

 description of the same species simultaneously by different observers. That 

 this overlapping must occur to some extent is inevitable. After our own 

 earlier investigations in H.M. shij)s Lightning and Porcupine, and those 

 of Count Pourtal^s in connection with the American Coast Survey, had 

 demonstrated the existence of a varied and remarkable fauna at extreme 

 depths, as well as the possibility of bringing the nature and distribution 

 of that fauna within the range of human knowledge, the' study of the bio- 

 logical conditions of the deep sea was rapidly and energetically extended. In 

 most cases this question has been made a national one, the extent and cost 

 of such explorations being beyond the ordinary limit of private enterprise, 

 and the American, the Swedish, the German, the Austrian, the Italian, and 

 the French Governments have already made valuable additions to our 

 knowledge. One systematic series of investigations requires special notice ; 

 for several years Professor Alexander Agassiz has undertaken successive 

 expeditions under the auspices of the United States Coast Survey, for 

 the purpose of observing the conditions of the Caribbean Sea and the Gulf of 

 Mexico. Results of these cruises of the highest interest are being published in 

 quick succession, and, for reasons which will be explained hereafter, many of 

 the species in different invertebrate groups procured by the Challenger are 

 described by the specialists who have undertaken the preparation of Mr 

 Agassiz's Reports. The extent of our collections makes the rapid publication 

 of the descriptions of the larger groups, and the discussion of the general 

 phenomena of distribution impossible, but the inconveniences arising from 

 delay may be reduced to a minimum by the plan which we have adopted. 

 Each Memoir will be paged separately, and a legend will be attached to each 

 by which it can be referred to ; for example (Zool. Chall. Exp. — Part I. — 

 1880). Each of the Zoological series of volumes, of which this is the first, 

 will contain one or more Memoirs, and will be published with a provisional 



