June, 1931 



EVOLUTION 



Page seventeen 



lasts from March through June, abun- 

 dant specimens of the wood frog, green 

 frog, leopard frog, pickerel frc^, and 

 the tiny tree toad an inch long, that in- 

 flates its throat like an amber bubble 

 and gives its clear shrill "peep." The 

 garden toad also joins this gathering, for 

 practically all amphibians frequent the 

 water to lay their eggs. Salamanders also 

 issue from their hiding places under 

 damp stones, and crawl to the water's 

 edge on the same errand. Here in the 

 warmth of the spring sun, the egg masses 

 pursue their course of development — 

 mysterious even though all its history 

 may be known — into the tadpole stage 

 characteristics of the species, and finally 

 attain the adult form. 



Next in the list of animal habitants 

 let us take land associations. Some of 

 these include animals of the surface 

 ground and animals living on vegeta- 

 tion. As you walk through the woods 

 you may be passing by some black-and- 

 white or yellow-spotted salamander hid- 

 den under a stone, or a tiny red-backed 

 salamander concealed under the bark of 

 a dead tree. Many forms of life can be 

 brought to light by turning over stones 

 and stripping bark from dead trees. 

 Your eyes will have to be sharp to find 

 signs of life upon bushes and trees. 

 Look for cocoons of moths, hanging like 

 dead leaves upon twigs. Examine green 

 leaves curled over to form the covering 

 for some insect eggs. You may find a 

 "walking-stick" which looks like a twig 

 until you see it move or discover dull- 

 colored moths resting upon the bark of 

 trees, perfectly camouflaged. Look for 

 cast-off skins of cicadas (incorrectly 

 called locusts) still adhering to the tree 

 trunks by ghostly claws, showing a split 

 down the back through which the iride- 

 scent adult burst its prison. 



Sharp eyes will find these things. It is 

 something at least to have found your 

 quarry, but don't stop there. Find out 

 something about its life history. Can you 

 follow it from the cradle to the grave? 

 How does it make its living? Do you see 

 any special value in any of its parts for 

 the kind of life it has to lead? You will 

 find zest now in planning a small na- 

 ture library to aid you in your quest. 

 Charts and pamphlets published by vari- 

 ous nature organizations are helpful and 

 inexpensive. Use these at home to round 

 out your study. Observation may reveal 

 ^what an animal does but not what it is. 



Best Evolution Pamphlet 



The clearest, simplest explanation of 

 Evolution is "The Proofs of Evolution" 

 by Henshaw Ward, excellent for be- 

 ginners and opponents. Sent postpaid 

 for 10c; 20 for ^1. 



Question Box 



Answers by Allan Broms, unless otherwise credited 



Q. — How do such meteorites as those 

 at the American Museum of Natural 

 History originate, and how do you ex- 

 plain that peculiar crystal structure inside 

 them? F. P. J. 



A. — These meteorites, as you know, 

 have fallen upon the earth from outer 

 space. Most "shooting stars" are much 

 smaller, mere grains of meteoric sand 

 that burn into ashes from the friction of 

 the air as they rush through it at speeds 

 up to 44 miles per second. The large 

 meteors can reach earth without burning 

 all up because the heat of friction on 

 their surfaces does not have time to 

 strike into the interior, but merely fuses a 

 thin outer shell. So this heat cannot 

 help us explain the internal crystalline 

 structure. 



T. C. Chamberlin, in his "The Two 

 Solar Families", has given us a reason- 

 able answer to both your questions. It 

 is well known that the "shooting star" 

 meteors, and the comets with which they 

 are associated, travel in long elliptical 

 orbits that take them alternately out into 

 the cold depths of space and then close 

 to the hot sun. They stay long out in 

 the distant zone of darkness and cold 

 where the sun's gravitational pull is 

 very feeble. So the fine dust specks and 

 larger meteoric grains have a chance to 

 gather into loose clumps under their own 

 mutual gravitational pulls, even though 

 these be very weak. Their collisions are 

 gentle, for the motions are very slow, 

 both in their orbits about the sun and 

 in their falls towards each other . Besides 

 they are out there in the feeding grounds 

 a long time before they return to the 

 vicinity of the sun. But as they head 

 sunward they fall, slowly at first, then 

 faster and faster, until they reach enor- 

 mous velocities in passing the sun. They 

 might well be broken up and dissipated 

 by the melting heat of the sun, but if 

 they are largely metallic, they instead 

 fuse and hang together. This probably 

 explains why most large meteorites are 

 metallic, composed of an iron-nickel al- 

 loy, with only a mixture of stony matter. 

 Such molten metallic masses, as they 

 slowly cool through the months of their 

 retreat into cold outer space, stay toge- 

 ther and tend to crystalize, explaining 

 the characteristic interior structure, which 

 when polished and etched by acid, reveals 

 the formerly mysterious Widmanstatten 

 figures to which you refer. Of course, 

 each time they pass through the outer 

 feeding grounds, they will add to their 



size, each sunward trip fusing the loose 

 matter so accumulated into the main 



meteoric mass. 



* * * 



Q. — Why are crocodile tears? J. C. 

 A. — Of course, I realize that you are 

 "kidding" me, but my comeback is to 

 give a sensible anwser to a foolish ques- 

 tion. Tears came into the lives of 

 crocodiles, other reptiles and all other 

 higher back-boned land animals because 

 they serve a useful purpose, give advan- 

 tage in the struggle for existence. For 

 crocodiles, even though they spend so 

 much time in the water, are land animals 

 in their physical structure. They breathe 

 with lungs all through life, have legs 

 for walking on land all through life, and 

 have eyes fitted to land life all through 

 life. The emphasis on "all through Ufe" 

 is to distinguish them from the am- 

 phibians, the frogs, newts and salaman- 

 ders, who start off as water-dwellers, 

 breathing with fish-like gills, and who 

 must change both structure and ways to 

 fit them for their adult land life. Their 

 very name, amphibians, tells that they 

 lead this double life. Everyone knows 

 that they represent the evolutionary 

 transition from fishes to the land dwell- 

 ing reptiles. Though the reptiles preserve 

 many old fish and amphibian features, 

 they are fitted only as lung-breathers 

 and sometime land-dwellers. They al- 

 ways, for instance, lay their eggs on dry 

 land and they have tears. 

 Those tears are a dry-land adaptation. 

 They substitute for the water in which 

 the fishes live and with which they wash 

 the dirt out of their eyes. They are never 

 troubled, as the reptile is, by dry-land 

 dust that gets in their eyes to torment 

 and obscure vision. Their eyes are get- 

 ting a perpetual eye-wash. When the 

 reptiles took definitely to the land, tears 

 came into the world, for eye-flushing 

 purposes only. Well developed eye-lids 

 helped too, by keeping the dust out, by 

 loosening it mechanically. But the tears 

 came for prosaic use not for sentimental 

 purposes as a mere eye-wash. The croco- 

 dile has no use for sentiment in his life. 

 It would interfere with his method of 

 getting a living. But he does have use 

 for tears. Of course, this does not ex- 

 plain the origin of that saying about 

 "crocodile tears", but that happens to be 

 another story. 



When you Renew, include an extra ^I. 

 for Evolution for some friend. 



Evolution, 175 Varick St., N. Y. C. 



