84: THE MICROSCOPE AND ITS REVELATIONS. 



Orbitolite ( 466), a series of chamberlets being concentrically arranged 

 round a ' nucleus'; and as the same appearance is presented, whatever be 

 the direction of the section, it becomes apparent that these chamberlets, 

 instead of being arranged in successive rings on a single plane, so as to 

 form a disk, are grouped in concentric spheres, each completely investing 

 that which preceded it in date of formation. The outer wall of each chuni- 

 berlet is itself penetrated by extensions of the cavity into its substance, 

 as in the Cyclammina last described; and these passages are separated by 

 partitions very regularly built up of sand-grains, which also close-in their 

 extremities, as is shown in Fig. 324. The concentric spheres are occa- 

 sionally separated by walls of more 



Fro 334 than ordinary thickness; and such a 



wall is seen in Fig. 323 to close-in the 

 last formed series of cjiamberlets. 

 But these walls have the same ' laby- 

 rinthic ' structure as the thinner ones; 

 and an examination of numerous 

 specimens shows that they are not 

 formed at any regular intervals. The 

 'nucleus' is always composed of a 

 single series of chambers arranged 

 end to end, sometimes in a straight 

 line, as in Fig. 323, c 1 , c*, c 3 , c*, some- 

 times forming a spiral, and in one 

 instance returning upon itself. But 



Portion of one of the lamellae or Parkerta, , , , -i v~ i % 



showing the sand-grams of which it is built up, tne outermost chamber enlarges, and 



and the passages extending into its subtance. extends itself OVC1' the whole ' nil- 



cleus,' very much as the 'circumam- 

 bient' chamber of the Orbitolite extends itself round the primordial 

 chamber ( 466); and radial prolongations given off from this in every 

 direction form the first investing sphere, round which the entire series 

 of concentric spheres are successively formed. Of the sand of which 

 this remarkable fabric is constructed, about 60 per cent consists of 

 phosphate of lime, and nearly the whole remainder of carbonate 

 of lime. Another large Fossil arenaceous type, constructed upon the 

 same general plan, but growing spirally round an elongated axis after the 

 manner of Alveolina (Fig. 315), and attaining a length of three inches, 

 has been described by Mr. H. B. Brady (loo. cit.), under the name Lof- 

 tusia, after its discoverer, the late Mr. W. K. Loftus, who brought it 

 from the Turko-Persian frontier, where'he found it imbedded in " a blue 

 marly limestone " probably of early Tertiary age. 



478. There is nothing, it seems to the Author, more wonderful in 

 Nature, than the building-up of these elaborate and symmetrical struc- 

 tures by mere 'jelly- specks,' presenting no trace whatever of that definite 

 ( organization ' which we are accustomed to regard as necessary to the 

 manifestations of Conscious Life. Suppose a Human mason to be put 

 down by the side of a pile of stones of various shapes and sizes, and to be 

 told to build a dome of these, smooth on both surfaces, without using 

 more than the least possible quantity of a very tenacious but very costly 

 cement in holding the stones together. If he accomplished this well, he 

 would receive credit for great intelligence and skill. Yet this is exactly 

 what these little 'jelly-specks' do on a most minute scale; the 'tests' 

 they construct, when highly magnified, bearing comparison with the most 

 skilful masonry of Man. From the name sandy bottom, one species picks 



