SCIENCE- GOSSIP. 



such as phosphorus, sulphur, Iron, and iodine, 

 whose known chemistry indicates considerable 

 dynamic possibilities. 



Silicon is still a fairly abundant constituent of 

 the living body, both of animals and vegetables. 

 Its chief function is to give rigidity to the frame- 

 work. There is no reason to think that its chemical 

 reactions contribute sensibly to the energy traffic, 

 or that it ever combines directly with any other 

 element than oxygen. 



The meteoric theory is the modern version of the 

 nebular theory. It is not customary nowadays to 

 regard nebulae as masses of hot gas. Evidence is 

 in favour of their being collections of matter of all 

 kinds, such as meteoric fragments, dust, and gases, 

 at a low average temperature. Light and heat are 

 produced by collisions of the fragments, but the 

 heat is lost by radiation so long as the material is 

 sparsely distributed. When, however, the material 

 condenses into compact masses, the heat of 

 collision and compression accumulates in the 

 interior of the masses, but escapes more or less 

 from their surfaces. Thus a sphere as large as the 

 sun produces heat enough internally to keep its 

 surface white-hot in spite of loss by radiation. 

 Jupiter can keep his surface perhaps barely red- 

 hot ; but a mass so small as the earth can produce 

 so little heat (in ratio to the loss by radiation) that 

 the surface is only " temperate." Since the mass of 

 a sphere varies with the cube of the diameter, while 

 the surface varies with the square of the same, it is 

 evident that the ratio of radiation to heat-produc- 

 tion must be greater in a small than in a large 

 world. Geological evidence indicates that the 

 earth's surface has been at about the same tem- 

 perature for many millions of years. It may have 

 been cooler at some period, and it may have been 

 warmer ; but we can hardly believe that the heat- 

 production of our little world could ever have been 

 sufficient to melt the rocks at its surface. 



A few miles below the surface, however, the 

 temperature may be high enough to melt any 

 known rock : and where great lateral pressure exists, 

 with consequent over-riding movements, fusion may 

 occur quite near the surface. This took place not 

 long ago, when the Alps, a comparatively recent 

 mountain group, were thrown up. Under the stress 

 the silica rose to the melting-point, reacted on the 

 adjacent minerals, and produced the granite which 

 forms the core of the mountains. For further in- 

 formation on the movements of the earth's crust 

 and the production of igneous rocks, I must refer 

 the reader to the works of the chief exponent of 

 the subject, Professor Lapworth. The nebular or 

 meteoric theory is lucidly explained in recent 

 publications by Sir Norman Lockyer. 



It is quite probable that in some parts of the 

 universe life originates " in a sea of white-hot 

 fluid " ; but geologists are less inclined than 

 formerly to believe in the existence of such a state 

 of things at any time on the earth's surface. Mean- 



while there is abundant evidence of the mainten- 

 ance of an. equable surface-temperature for n vast 

 period ; and it behoves the biologist to try whether 

 the known conditions would suffice to produce life 

 as we know it. To begin with white-hot matter is 

 to investigate from the wrong end. We must com- 

 mence with known conditions: it' these be found 

 insiillicient, we may go >tep by step into the hypo- 

 thetical, and may ultimately arrive at the stage of 

 white heat. For my own part, I am simple enough 

 to believe that the circumstances which support 

 life would also favour its origin. 



Beech Lawn, Link Common, Malvern, 

 July 12, L900. 



NOTES ON SPINNING- ANIMALS. 



By H. Waems Kew. 



(Continued from page 38.) 



III. Spinning Crustaceans. 



- 1 - r« 



T will probably come as a surprise to many 

 readers to know that a faculty of spinning 

 obtains among Crustaceans. Such, at least, was 

 the feeling of the present, writer on first hearing 

 of the facts now re-stated. 



SPIXXIXIi-I.El! OF AMPHIPOD-SIIRIMP ('). 



The Crustaceans to which we refer are those of 

 the order Amphipoda (Amphipod-shrimps), animals 

 of small or moderate size ; mostly marine, but 

 more generally known, perhaps, from their fresh- 

 water or semi-terrestrial representatives, such as 

 Gammar us, the fresh-water shrimp, and Talitrus, 

 the sand-hopper. A very large number of these 

 animals walk, hop, or swim from place to place 

 without making, as far as is known, any definitely 

 constructed home. There is, however, on the 



(1) One of the third pan- of legs of Xenoclea megachir, with 

 the epimeron ami trill, seen from the outside, and showing the 

 glandular organ within. (Enlarged 20 diameters.) ". The tip of 

 the dactylus, showing the perforation. (Enlarged lOo diameters. > 

 After S. I. Smith, "Transactions of the Connecticut Academy of 

 Arts and Sciences," lii. (1874), pi. III. fig. 3. 



i>4 



