SCIENCE-GOSSIP. 



to show that the struggle is largely so, and that 

 those which survive are the most fit only in the 

 sense that those who survive in a railway accident 

 or earthquake are the fittest. 



Mr. Reid brings forward many arguments 

 against the transmission of acquired characters — 

 that is, against the view that acquired characters 

 produce exactly the same characters in the 

 offspring. From the force of these arguments 

 there seems to be no escape ; but in a subsequent 

 chapter it is admitted that acquired characters 

 may, and must, influence the offspring, though not 

 to reproduce the effects produced on the parent. 

 Yet it is hard to resist the conviction that some 

 of the arguments adduced in the former case tell 

 equally against the latter view. 



The persistence of many extremely low forms of 

 life, while others have advanced to such a degree 

 of complexity, has been often felt to be a difficulty. 

 To explain how certain species have continued 

 in their low estate, in spite of the evolution 

 around them. Mr. Reid brings forward the 

 following somewhat misleading analogy : " The 

 upward march of life from the earliest begin- 

 nings may be compared to that of a horde of 

 men leaving their old habitations and entering 

 new lands ; travelling ever forwards, but ever 

 sending out branch swarms that part from the 

 parent horde, never to reunite with it, and ever 

 leaving some of their members behind on the way, 



some of whom may journey backwards 



The lowest, or in other words, the least differ- 

 entiated and specialized, forms of life may be 

 compared to those members of the horde that 

 stayed behind in the original habitat, the inter- 

 mediate forms to those that halted and settled by 

 the way, and the highest forms to those that 

 journeyed till they reached the farthest limits 

 of the wanderings." This analogy is misleading ; 

 for being left behind in the struggle for life 

 means extermination, according to the principles of 

 natural selection. The strict analogy between the 

 production of species in nature "and the production 

 of varieties artificially, is insisted upon. Existence 

 of domestic breeds seems to be looked upon as 

 proof that evolution by natural selection can take, 

 and has taken, place in nature ; but we are not 

 told how the part played by man in isolating his 

 breeds and preventing crossing is effected in nature. 

 The instability of domestic varieties as compared 

 with the stability of natural species seems also to 

 be left out of consideration. That man, by care- 

 fully mating like with like, as well as selecting, can 

 produce an unstable variety, is no argument that 

 selection alone in nature can produce a stable 

 species. 



On reaching Part II. we come to Mr. Reid's views 

 as to what natural selection is now doing for man, 

 and which gives the work its title. When Ceres 



wished to benefit the sick youth Triptolemum, she 

 — his mother's back being turned — set him down 

 in the glowing embers of the fire to burn out his 

 mortal parts. According to Mr. Reid, natural 

 selection is playing the part of Ceres to the human 

 race, by exposing it to the risk of infection, and 

 gradually weeding out the susceptible part. 

 Susceptibility to disease is a variable quality : 

 those who have it in the highest degree will be 

 the least fitted to survive, and will therefore be 

 gradually weeded out. Thus natural selection will 

 tend to produce a disease-proof race. 



Let us then examine a few of Mr. Reid's facts 

 and arguments. In regard to malarial fevers and 

 other diseases of hot countries which are so fatal 

 to Europeans, it is pointed out that the natives 

 enjoy a certain immunit)'. It is, therefore, claimed 

 that the race is being evolved in the direction of 

 immunity, continual exposure to infection weeding 

 out the more susceptible. Careful examination is 

 requisite before we can accept the fact as evidence 

 for the theory. Thus it may well be that the 

 adults are less susceptible because they have had 

 the disease in childhood. Mr. Reid himself points 

 out that the natives themselves are more suscep- 

 tible in the early stages of life. Again, it is quite 

 possible that the native manner of life is such as 

 to help them to resist the disease. When due 

 allowance has been made for these, and possibly 

 other factors, it will, perhaps, scarcely be necessary 

 to invoke acquired immunity to account for the facts. 



Again, among ourselves, many diseases have 

 certainly diminished, and this appears to favour 

 the view that the human race is acquiring 

 immunity. For this reduction improved sanitary 

 arrangements, and the progress of medicine claim 

 a large share. In the case of small-pox, we have 

 three claimants to the chief share. The improve- 

 ment, say the vaccinators, is due to vaccination ; 

 it is due to improved sanitation say the anti- 

 vaccinators ; while Mr. Reid claims it for acquired 

 immunity. When due allowance is made for all 

 other probable or possible causes, it is difficult to 

 say how much is left for acquired immunity. Mr. 

 Reid has not even attempted the task. 



Much stress is also laid upon the fact that 

 uncivilized nations suffer more severely from 

 the diseases introduced by civilization than those 

 civilized nations that have introduced them, and 

 which have themselves acquired immunity. This 

 severer suffering is supposed to imply that to the 

 natives it is a new disease, and they have not been 

 evolved against it. Mr. Reid does not, however, seem 

 to have set himself to inquire whether the diseases 

 are really new to them or not. Is there evidence, 

 for example, to show that consumption is a new 

 disease to any uncivilized nation ? Again, Mr. 

 Reid ignores the fact that the greater mortality 

 among savages from the so-called diseases of 



