OF GAL WAY. 21 



each other, and thus form a Hving network, along the various lines 

 of which the granular matter of the protoplasm flows freely. 

 This circulation differs from that in the hair of a sting-nettle, 

 where it is confined by the lining membrane of the cell-wall, or 

 the fovilla in the pollen tube, inasmuch as it is not confined by a 

 membrane, but circulates on the outside of a viscous network in 

 the medium of salt or brackish water. 



When any prey, such as a minute diatom, touches this net, it 

 adheres, more protoplasm flows over and embeds it ; the nutriment 

 is absorbed and the refuse rejected. Thus nourishment goes on 

 outside the shell. 



Except in the one- celled Foraminifera, as the animal grows it 

 adds fresh chambers, each being generally larger than the last, the 

 aperture of which forms its centre of origination as its own 

 aperture forms its completion. Thus, from the earliest to the last 

 segment, one opens into the next, whilst the creature inhabits 

 them all simultaneously.'*' These organisms are found all over the 

 ocean bottom. They are to be met with on every seashore, whilst 

 some forms are more peculiarly plentiful in brackish water. 



The shells are of three principal structures : — The Porcellan- 

 ous, or opalescent, are white by reflected, amber-coloured by 

 transmitted light. These emit their pseudopodia in a branching 

 trunk from one aperture, but have no foramina. 



The Hyaline, when young, are like glass becoming white or 

 semi-opaque with age. These are foraminated, emitting pseudo- 

 podia from these pores, as well as by their aperture, and sometimes 

 investing their shell in sarcode, which emits the pseudopodia. 

 These two groups are calcareous. 



The third kind are Arenaceous, or made up of grains of sand 

 cemented together. These are frequently silicious — boiling liquor 

 potassce^ in most cases, does not dissolve the cement by which they 

 are formed. These are often tinged, more or less, brown or 

 orange by the oxide of iron probably, as intimately associated 

 with the protoplasm of these minute organisms as with that of the 

 higher developments of the entire vegetable and animal kingdoms. 



Of these microscopic shells in the deep oceans and shallower 



* See Williamson's Foraminifera, Ray Society, 1858, for further details, and 

 Carpenter's Introduction to Foraminifera. 



