NOTES ON RETICULARIAN RHIZOPODA. 31 



with greater force than to the Rhizopoda, and it seems desir- 

 able, therefore, that some of the more interesting facts and in- 

 ferences which have been already acquired should be made 

 the subject of a preliminary notice. 



I propose in the present, and perhaps in one or two sub- 

 sequent papers, to give a brief, and in some respects a pro- 

 visional description of certain new or little understood types 

 of E-hizopoda, indicating the lines in which additions to our 

 knowledge of the group are furnished by the " Challenger" 

 collections, rather than to attempt anything in the way of 

 systematic history, which can only be rightly done when the 

 results come to be treated collectively and in detail. I shall 

 confine myself to the consideration of types actually obtained 

 in this Expedition, except in one or two instances in which 

 specimens from other sources seem to supply missing links, or 

 otherwise assist in the elucidation of morphological pecu- 

 liarities. 



The list of observing stations drawn up and printed for the 

 use of those engaged in working out the natural history of 

 the Expedition extends to 354 localities. Some of these are 

 represented by mere soundings, of which only a small reference 

 sample of the bottom was preserved, whilst a few include 

 several dredgings made on the same or successive days within 

 a restricted area. Not unfrequently a number of consecutive 

 dredgings in mid-ocean at similar depths are practically 

 identical in their organic constituents, and again, the 

 physical characters of a certain number of the samples are 

 not sufficiently promising to warrant the expenditure of 

 much time over them, so that it has been necessary to make 

 a selection from the series. About fifty dredgings, represent- 

 ing conditions as diverse as possible, were taken in the first 

 place for complete examination, and by the light of the 

 results obtained from these, further selections w^ere made 

 from time to time, until altogether about 140 have been 

 exhaustively worked out. By " exhaustively" I mean that 

 the sand or mud was washed^ to begin with, on a sieve of the 

 finest wire gauze (that known as No. 120), the meshes of 

 which were something less than^^o^th of an inch in diameter. 

 Practically it was found that what passed through this sieve 

 was for the most part veritable mud, composed either of fine 

 inorganic particles, or of the impalpable debris of calcareous 

 tests of one sort or other. Cocoliths were usually present in 

 this finest material, occasionally also the frustules of Diato- 

 mac(S, and more commonly the siliceous skeletons of the 

 minute species of Radiolaria, but for the Reticularian Rhi- 

 zopoda it was of little value ; not because it did not 



