96 



NATURE 



\yune I, 1876 



crests between 'the pores are much less regular in Orbu- 

 Una than they are in Globigerina ; and the spines, which 

 are of great length and extreme tenuity, seem rather to 

 arise abruptly from the top of scattered papillae than to 

 mark the intersections of the crests. This origin of the 

 spines from the papilte can be well seen with a moderate 

 power on the periphery of the sphere. The spines are 

 lioUowand flexible ; they naturally radiate regularly from 

 the direction of the centre of the sphere ; but in specimens 

 which have been placed under the microscope with the 

 {greatest care, they are usually entangled together in 

 twisted bundles. They are so fragile that the weight of the 

 shell itself, rolling about with the motion of the ship, is 

 usually sufficient to break off the whole of the spines and 

 l:ave only the papilla; projecting from the surface in the 

 c'urse of a few minutes. In some examples, either those 

 in process of development, or a series showing a varietal 

 divergence from the ordinary type, the shell is very thin 

 and almost perfectly smooth, with neither papillae nor 

 spines, nor any visible structure except the two classes of 

 pores, which are constant. 



The Coccospheres and Rhabdospheres— these are 

 suggested to be minute algas forms — live on the surface, 

 and sink to the bottom after death. Many of them are 

 extremely beautiful, as will be seen from Figs. 4 and 5, 

 representing two forms first discovered by Mr. Murray. 



Taking the section from Teneriffe to Sombrero, first of 

 all some 80 miles of volcanic mud and sand were passed ; 

 then some 350 miles of globigerina ooze ; next about 

 1,050 miles of red clay; then again a rising ground for 

 some 330 miles of globigerina ooze, a valley of 850 of red 

 clay ; and nearing land some 40 miles of the globigerina 

 ooze. Intermediate between the red cliy and the globi- 

 gerina ooze, a grey ooze was met with, partaking of the cha- 

 racters of both, and evidently a transitional stage. " There 

 seems to be no room," writes Prof. Wyville Thomson, "left 

 for doubt that the red clay is essentially the insoluble resi- 

 due, the ash, as it were, of the calcareous organisms which 

 form the ' globigerina ooze,' after the calcareous matter has 

 been by some means removed. An ordinary mixture of 

 calcareous Foraminifera with the shells of Pteropods, 

 forming a fair sample of ' globigerina ooze ' from near St. 



Fig. 4 — Rhabdosphere. 



Thomas, was carefully washed and subjected by Mr. 

 Buchanan to the action of weak acid ; and he found that 

 there remained, after the carbonate of lime had been 

 removed, about one per cent, of a reddish mud, con- 

 sisting of silica, alumina, and the red oxide of iron. This 

 experiment has been frequently repeated with different 

 samples of * globigerina ooze,' and always with the 

 result that a small proportion of a red sediment remains, 

 which possesses all the characters of the ' red clay.' I 

 do not for a moment contend that the material of the 

 * red clay ' exists in the form of the silicate of alumina and 

 the peroxide of iron in the shells of living Foraminifera 

 and Pteropods, or in the hard parts of animals of other 

 classes. That certain inorganic salts other than the salts 

 of lime exist in all animal tissues, soft and hard in a cer- 

 tain proportion, is undoubted ; and I hazard the specu- 

 lation that during the decomposition of these tissues in 

 contact with sea-water and the sundry matters which it 

 holds in solution and suspension, these salts may pass 

 into the more stable compound of which the ' red clay ' 

 is composed." 



On this voyage Mr. Buchanan found the remarkable 



Fig 5. - Rhabdospliere. 



and unexpected result that the water has virtually the 

 same specific gravity from the bottom to within 500 

 fathoms of the surface. From 500 fathoms the specific 

 gravity rapidly rises till it usually attains its maximum at 

 the surface. Nineteen dredgings were taken, and these 

 yielded a large supply of animal forms. It is unfortunate 

 that in the deepest haul of all, 3,150 fathoms, no living 

 thing was brought up higher in the scale than a fora- 

 minifer ; but this may be attributed to the nature of the 

 bottom, an opinion borne out by the abundance, at 

 scarcely a less depth, and on a bottom differing only in 

 being somewhat less uniform, and containing sand-grains 

 and a few shells of foraminifera, of tube building annelids 

 of a very common shallow water type. The Crustacea 

 do not appear to suffer from the peculiarity of the circum- 

 stances under which they live, either in development or 

 in colour. The singular fact of the suppression of the 

 eyes in certain cases is already well known. The 

 Echinoderms and sponges which enter so largely into 

 the fauna of the zone ending at i,coo fathoms are not 

 abundant at extreme depths. 

 The Challenger next anchored off the harbour of Char- 



