April 15, 1880] 



NATURE 



569 



DEEP-SEA DREDGING AND LIFE IN THE 

 DEEP SEA • 



II. 



THE surface-water of the ocean is inhabited by an 

 abundant animal fauna peculiar to itself, and termed 

 pelagic. In ubiquity of geographical distribution the 

 animal forms composing this fauna approach very nearly 

 the fauna of the deep-sea bottom. There appears to be a 

 marked relation between the pelagic fauna and the deep-sea 

 fauna. Almost all the deep-sea forms have closely-allied 



Pelagic Glcblgerina. Much magnified. 



representatives floating or swimming near the ocean sur- 

 face. The deep-sea sea-anemonies are represented on the 

 surface by floating sea-anemonies. There are surface- 

 worms, hydroids, bryozoa, barnacles, and fish represented 

 by close allies on the deep-sea bottom. Lastly, there are 

 abundance of surface Rhizopoda corresponding with the 

 vast quantities of them below (Fig. 10). 



1 Friday Evening Lecture delivered at the Royal Institution on March 5, 

 by H. N. Moseley, F.R.S., Assistant Registrar of the University of London. 

 Continued from p. 547. 



Here is one of these surface Rhizopods, a Globigerina 

 which, like most, but not all, of the Globigerinae occurring 

 at the surface, is covered with delicate calcareous spines 

 projecting from its shell. That the deep-sea bottom is 

 over vast areas covered by a mud composed mainly of 

 Globigerina shells like this one, but without the spines, is 

 well known to all my hearers. 



An important question which has been much disputed 

 is, whether the Globigerina mud is entirely derived from 

 the surface, being made up of dead shells fallen from 

 above, or whether the shells composing it live on the 

 bottom. Mr. Henry Brady, after 

 examining all the Challenger col- 

 lections, concludes that the main 

 components of the mud do live on 

 the bottom. Certain species found 

 there do not occur on the surface at 

 all, and Globigerina; occur on the 

 bottom near our own shores, where 

 none have ever been found on the 

 surface. Further, the shells of the 

 specimens found on the deep-sea 

 bottom are much larger and thicker 

 than any yet found on the surface. 

 Here are some deep-sea Rhizopoda, 

 concerning which there has never 

 been any doubt as to their living 

 on the deep-sea bottom. Dr. Car- 

 penter described many such long 

 ago. The accompanying illustra- 

 tions (Fig. 11, a, b, c) are from Mr. 

 Brady's figures. These Rhizopods 

 ire called arenaceous, because their 

 shells are mostly made up of sand 

 particles and foreign bodies of all 

 kinds glued together. These arena- 

 ceous Rhizopods are abundant all 

 over the world, and reach down to 

 the greatest depths. One, shown 

 in the figure (<z),from 2,760 fathoms, 

 has included sponge spicules in its 

 test. Another one (i) is from 2,900 

 fathoms. It is chambered some- 

 what like a Globigerina. This other 

 one (/) is attached to a heavy body, 

 a sufficient evidence, were any re- 

 quired, that they lived on the 

 bottom. 



Supposing that Globigerina; do 

 live at the bottom as well as at the 

 surface, do they also live at inter- 

 mediate depths ? This opens the 

 most important question which at 

 present remains to be solved with 

 regard to deep-sea life. It applies 

 not only to Globigerina;, but to all 

 the vast pelagic fauna to which I 

 have referred. Do the jelly-fish, 

 the Crustacea, the mollusca, and 

 other animals so abundant in sur- 

 face waters inhabit also the depths 

 of the mid-ocean, or is there a vast 

 azoic area between the surface and 

 the bottom untenanted by life in any 

 form ? To this question we can at 

 present return no answer of any value. The trawls used 

 by the Challenger swept, in going down to the bottom and 

 coming up again, the whole stretch of the :ea from top to> 

 bottom, and it is impossible to tell whether pelagic animals 

 found in it when it reached the surface were caught there 

 or at the bottom. Mr. Murray used the towing-net at 

 various depths, but the same objection applies to the 

 results. Deep-sea Medusae have been described by Prof. 

 Haeckel and deep-see Siphonophora by Prof. Studer, but 

 both may have come from very small depths. 



