Sea-hottom procured by II.M.S. ^ Ckallewjcr.'' 295 



a like replacement is going on at the present time, the chambers 

 of recent Foraininifora being occasionally found to be occupied by 

 aiineral deposit, which, when the sliull has been dissolved away 

 by dihite acid, presents a perfect internal cast of its cavities, liy 

 the apphcation of this method to Mr. Beete Jukes's Australian 

 dredgujgs, my coadjutors, Messrs. VV^ K. Parker and T. liupert 

 Jones, obtained a series of mternal casts of most wonderful beauty 

 and completeness, on which 1 have based my interpretation of the 

 organic structure of Eozuua canadense. Having myself examined 

 in the same manner a portion of the I'oraminiteral sand dredged 

 by Capt. Sprat t in the vEgean (kindly placed in my hands by Mr. 

 J. Gw}na Jelfreys), 1 have found that it yielded a great variety of 

 these beautiful models, not only of the bodies of 1 oraminifera, but 

 also of the sarcodic network which interpenetrates the calcareous 

 network of the shell and spines of Echinida*. 



Alike in Mr. Jukes's and in Capt. Spratt's dredgings, some of 

 these casts are in yreen silicates ami some in ochreous, corresponding 

 precisely to the two kinds of fossil casts described by Prof. Ehren- 

 berg. The dittereuce 1 presume to depend upon the degree of 

 oxidation of the iron; but as these casts are far too precious to be 

 sacriliced for chemical analysis, I cannot speak with certainty on 

 this point. 



As it is only in certain limited areas of the sea-bottom that this 

 replacement of the sarcodic bodies of Eoraminifera by mineral 

 deposit is met with, it has always seemed to me next to certain 

 that there must be some pecuUarity in the composition of the sea- 

 water of those areas (produced, perhaps, by the outburst of sub- 

 marine springs highly charged with ferruginous silicates) which 

 gives to them a capabiUty that does not exert itself elsewhere ; 

 and this now seems yet more probable from the circumstance that, 

 notwithstanding the vast extent over which the 'Challenger' 

 sountUngs and dredgings have been prosecuted, only two or three 

 cases of the kind have been noted — those, namely, of the " green- 

 ish sands' brought up from 98 and 150 fathoms in the region 

 of the Agulhas Current and in one or two other localities. It is 

 a fact of peculiar interest, moreover, that the calcareous shells 

 should have here disappeared, just as they have done in ordinary 

 green-sand — and this, too, although the depth was so small as 

 altogether to forbid the idea that their disappearance is due to any 

 solvent process brought about by the agencies to which Prof. 

 Wyville Thomson attributes the removal of the calcareous deposit 

 generated by Globigerine life. 



jS'ow, in the residue left after the decalcification of Capt. Spratt's 

 dredgings, 1 noticed a number of small particles of red ckiij, some 

 of them presenting no definite shape, whilst others approximated 

 sulUciently closely in form and size to the green and ochreous 



* Of these I hope to be able, ero long, to give a detailed account, in illns- 

 tration of the similar models of the animal of tkicoon obtained by the decalci- 

 flcation of its serpentine himelLe. 



