EECEEATIYE SCIENCE. 



147 



lest we should become too discursive, to con- 

 fine ourselves to one class, and, from their 

 great antiquity, the Foraminifera hold the 

 first claim to our attention. 



All are familiar with the household 

 sponge, and it is now very generally known 

 that sponge, with its curious tissue of inter- 

 lacing fibre, is but the horny skeleton of a 

 marine animal of the lowest condition of 

 life ; the like horny skeletons of small British 



9 



Hyaline-shelled Foraminifera (Globular arrange- 

 ment, running into Nautiloid). 

 Fig. 8, Orbulina universa, D'Orbigny. 9, Globigerina 

 buUoi'des, D'Orb. 10, Rotalina Partschiana, D'Orb. 

 ] 1, Polystomella Fichtelliana, D'Orb. 12, P. Eegina, 

 D'Orb. 



sponges are commonly cast by the waves on 

 our beaches. But still few know the animal 

 itself of the sponge, or would recognize what 

 it was if they saw it. The investing animal 

 substance of these homy skeletons was a 

 soft thin jelly, called by naturalists " sar- 

 code." It possessed no visible muscular 

 structure, and yet it had some slight power 

 of contraction and expansion, some slight 

 capacity of voluntary movements. Through 

 the smaller pore-like cavities with which the 

 skeleton of the sponge is seen to be per- 

 forated, the ocean-water was inhaled in a 

 current produced by the paddle-action of the 

 numerous minute cilia (or thread-like disten- 

 sions of sarcode) with which the internal 

 surfaces of those channels were lined, while 

 the water thus inhaled was expelled by the 

 fewer and larger tubular orifices denomi- 

 nated oscula. The sponge itself was rooted 



to one spot from the period of its first settle- 

 ment — for while young as a gemmule it swam 

 freely about — to the end of its life, and the 

 sponge of commerce is no more, as we haye 

 said, than the mere framework of the crea- 

 ture, which, dredged from its native depths, 

 has been kicked and trodden and blown 

 about, on the sands of the Mediterranean, 

 until every particle of its animal substance 

 has been wasted and destroyed ; and the 

 dust, so fuU of exquisite microscf<pic objects, 

 which we shake out from the fibrous net- 

 work, is nothing more than the sand of those 

 sea-shores, and not particles of food, as has 

 been sometimes ignorantly supposed. Dr. 

 Bowerbank has observed that the jelly-like 

 sarcode of the sponge can form itself into 

 temporary stomachs, into which the food 

 brought in by the inhalent currents of water 

 is received, digested, and assimilated, after 

 which the sarcode resumes its smooth, jelly- 

 like appearance, — so simple is the organiza- 

 tion of the sponge-animal ! 



The fibrous structure of fossil sponges of 

 a high class, the ventricalities, is beautifully 

 preserved in the flint nodules of the chalk, 

 and exhibits under the microscope wonderful 

 and remarkable designs, as has been admi- 

 rably elucidated by Mr. Toulmin Smith. 



The jelly-flesh condition is not confined 

 to the sponge; other animals having free 

 locomotion are formed of it. That micro- 

 scopic " proteus " the Amoeba is nothing 

 more than an atom of such sarcode. It has 

 no cilia, no power of swimming ; but if we 

 watch it, bud-like knobs are seen to be slowly 

 protruded from its body and gradually ex- 

 tended into pseudopodia, or false feet, more 

 than equal to the diameter of the body (see 

 woodcut, p. 145, Pig. 1). The ends of these 

 artificial limbs attach themselves sucker-like 

 to the surface over which the creature is 

 travelling, contract, and thus gradually drag 

 up the body (see woodcut, p. 145, Fig. 2). 

 Again, elongating knobs are protruded into 

 feeler-like limbs, which again, contracting like 



