HARDWICKE'S SCIENCE-GOSSIP. 



37 



It is in these these two famiUes that we find the 

 Foraminifera so closely resembling in their exterior 

 aspect the beautiful chambered shells of the Nautilus, 

 the Argonaut, and the fossil Ammonite, that little 

 wonder that the earlier naturalists actually classed 

 them together, whereas, indeed, they are as widely 

 separated as are the shrubs and flowers of the vege- 

 table kingdom from the humble nostoc. The in- 

 habitants of the former — creatures highly organised — 

 dwell only in the last-formed and largest chamber, 

 united with those previously inhabited by a tube or 

 siphon — whereas the Foraminifera occupies every 

 chamber, communication between each being afforded 



send off ramifications of smaller, which form a net- 

 work for circulation of fluid. The margin of the 

 shell is formed by a tube or siphon, which is the 

 medium of communication between the chambers. 



The sieve-like structure frequently presented by the 

 external shell is well seen in the beautiful Rosalina 

 (Fig. 23), and in a most exquisite form I rarely meet 

 with in Sponge sand (Fig. 24). This latter is the 

 most beautiful that I have seen, the steel-blue tint 

 not impairing its transparency, and the margin of 

 each of the foramina appearing golden, even when 

 viewed under a tolerably high power. 



Notwithstanding the simplicity of their structure — 



Fig. 22. — Portion of a slide of Foraminifera, from Sponge of Commerce. 



by the perforations (foramina) in the septa. Figs. 23 

 and 24 exhibit characteristic specimens of this group. 



Then, again, .we have a group in which the seg- 

 ments are added in concentric rings, each surround- 

 ing its predecessors. As an example may be men- 

 tioned the Orbitolites. 



Some of these minute shells are opaque, or some 

 opaque and homogeneous, some are arenaceous, i.e. 

 composed of particles of sand cemented by shell 

 material ; others again are exquisitely hyaline, i.e. 

 glass-like, and tubuliferous. 



The minute delicacy of structure frequently pre- 

 sented in these beautiful shells is well seen in the 

 Operculina, each chamber being separated from its 

 neighbours by double walls containing tubes, which 



if structure it can be called— these creatures neverthe- 

 less possess some capacity of voluntary movement. 



Place a living one in a vessel of water and examine 

 it with a hand magnifier. See how the tiny thing 

 emits, through the minute orifices in its habitation, 

 sarcode threads of wondrous tenuity, which adhere 

 to the sides of the vessel and seem to feel their way. 

 Is it seeming only ? Now and again these 'threads, 

 or pseudopodia, come into contact, and, lo ! as one 

 thread of liquid glue would coalesce with another, so 

 these life-endowed jelly threads immediately coalesce, 

 sometimes forming lakelets of sarcode ; the threads 

 behind are gradually withdrawn, and by means of the 

 foremost the creature slowly— painfully slow, so it 

 appears to us, we who so often erroneously associate 



