Dec. 



12, 



1889] 



NATURE 



129 



Uthough Mr. Cope offensively implies that they do not, viz. 

 '" Selection cannot be the cause of those conditions which are 

 [prior to selection : in other words, a selection cannot explain the 

 origin of anything." How can Mr. Cope presume to tell us 

 this? Who has ignored it? when? and where? Mr. Cope 

 does not seem to be aware of the fact that the anti-Lamarckians 

 attach great importance to the existence of congenital variation, 

 that Darwin himself has written at length on the subject, and 

 that Weismann has developed a most ingenious theory as to the 

 relation of fertilization and its precedent phenomena to this all- 

 important factor in evolution. 



Mr. Cope puts aside all that has been done on that subject, or 

 else is ignorant of it, and calmly lays down the following pro- 

 position : "If whatever is acquired by one generation were not 

 transmitted to the next, no progress in the evolution of a 

 character could possibly occur. Each generation would stnrt 

 exactly where the preceding one did." The full significance of 

 this sentence can only be apprehended when it is understood 

 that Mr. Cope believes that progress in the evolution of a 

 character does occur. The statement therefore amounts to this : 

 (i) that whatever is acquired by one generation is transmitted to 

 the next ; and (2) that the only possible explanation of the fact 

 that a new generation does not exactly resemble its parents at a 

 corresponding age is that the parental generation has transmitted 

 to its offspring particular features acquired by it between birth 

 and maturity. 



I doubt whether Mr. Cope will find any other naturalist — 

 even the most ardent Lamarckian — to join him in these 

 assertions. 



With regard to the first, it is hardly necessary to say that it 

 has never yet been shown experimentally that «//j'M///^'- acquired 

 by one generation is transmitted to the next (putting aside para- 

 sitic diseases); and as to evoytJiing ("whatever") being so 

 transmitted, every layman knows the contrary to he true. 

 Children are not born with the acquired knowledge of their 

 parents. If there were no other explanation offered of offspring 

 varying from their parents at a like age than the hypothesis of 

 transmission of characters acquired by the parents on their way 

 through life by the action of the environment, this hypothetical 

 explanation would still be quite insufficient to account for the 

 fact that the individuals of one brood vary enormously as com- 

 pared with one another, a fact which points to the individual 

 germs (egg-cells and sperm-cells) as the seat of the processes 

 which result in variation, and not to the parental body which 

 is the common carrier of them all. Assuredly these l>roods 

 demonstrate that all the acquired characters are not transmitted 

 to all the offspring. 



With regard to the second proposition which Mr. Cope's 

 statement contains, experimental fact is directly opposed to its 

 truth. As cited by Darwin on p. 8 of the first edition of the 

 "Origin of Species," Geoffroy St. Ililaire showed that "un- 

 natural treatment of the embryo cau-es monstrosities ; and 

 rnonstrosities cannot be separated by any clear line of distinc- 

 tion from mere variations." Mr. Darwin himself was "strongly 

 inclined to suspect that the most frequent cause of variability 

 may be attributed to the male and female reproductive elements 

 having been affected prior to the act of conception." What he 

 meant by " being affected" is. explained at greater length in 

 the " Animals and Plants under Domestication," where, in 

 chap, xxii., there is a long discussion of the causes of variability, 

 the conclusions of which are supported by an array of observed 

 facts which Mr. Cope cannot he permitted to ignore at his 

 pleasure. Mr. Darwin there gives solid reasons (as was his 

 wont) for holding that variability results from the conditions to 

 which the parents have b?en exposed : changes of any kind in 

 the conditions of life, even extremely slight changes, often suf- 

 fice to cause variability. But Mr. Darwin's examination of the 

 facts did not lead him to conclude that the bodily characters 

 acquired by the parents as the result of changes were those 

 which manifested themselves as variations in the offspring. On 

 the contrary he showed that the effect of changed conditions, of 

 excess of nutriment, and of the crossing of distinct forms, is a 

 "breaking down," as it were, of the hitherto fixed characters 

 of the race, leading to the reappearance of long-1 ist characters 

 and to the appearance of absolutely new characters, the new 

 characters having no more (and perhaps not less) relation to the 

 exciting cause which acted through the parent than has the 

 newly-formed pattern in a kaleidoscope to the tap on the 

 kaleidoscope tube which initiated the rearrangement. 



For Mr. Cope to complain of the methods of reasoning of 



post-Darwinians, and at the same time without any reasoning 

 at all to assert (as he does, not directly but by implication) that 

 there is no such thing as "congenital variation " or "sporting," 

 is not quite satisfactory. When it is asserted that every feature 

 by which a young animal differs from the structure of its parents 

 at a corresponding age must have been acquired by one or other 

 of the parents as actual structural features, and so transmitted as 

 an acquired character to the offspring, the whole world of fanciers, 

 horticulturists, farmers, and breeders, is ready with its unanimous 

 testimony to contradict the assertion. 



Let me say, in conclusion, that, as Mr, Wallace has pointed 

 out, Mr. Darwin did not consider that variability in a state of 

 nature was either so general or so wide in its range as later 

 observations and reflections lead us to believe it to be. Mr. 

 Darwin studied those causes which are found by practical 

 gardeners and breeders to be favourable to excessive variation 

 in animals and plants under domestication. He showed clearly 

 that the resulting variations had no adaptive relation to the 

 exciting causes, and were manifested in the structure at birth of 

 a new generation, and not in that of the generation suf)jected to 

 the exciting cause. No one has yet been able to give an 

 adequate account of the frequency and range of variation of any 

 number of animals or plants in a state of nature, because natural 

 conditions destroy, on the average, all individuals born of two 

 parents — except two — before maturity is reached, and those two 

 are naturally selected in consequence of their adhesion to the 

 specific type. 



There can Ise no doubt from a consideration of the facts cited 

 by Darwin that, whilst variation often is reduced to a miniiiiuin 

 in natural conditions which remain constant, natural variations 

 of conditions can and do occur, which excite the germ-cell and 

 sperm-cell, or their united product, to vary as in conditions of 

 domestication. There can be no doubt that there was in 

 Mr. Darwin's mind the conception of a definite relation 

 between two effects arising from changed conditions : the 

 one being the disturbance of the equilibrium of the organism 

 and its consequent production of variations ; the other 

 being the new requirements for survival ; in fact, there 

 seems to be, as it were, at once a new deal and new rules 

 of the game. It is not difficult to suggest possible ways in 

 which the changed conditions shown to be important by Darwin 

 could act through the parental body upon the nuclear matter of 

 ^gg'cell and sperm-cell, with its immensely complex and there- 

 fore unstable molecular constitution, so as to bring about varia- 

 tions (arbitrary, kaleidoscopic variations) in the ultimate product 

 of the union of the remnant of the twice-dividtd threads of the 

 egg-nucleus with the nuclear head of a spermatozoon. The 

 wonder is, not that variation occurs, but that it is not exces.sive 

 and monstrous in every product of fertilization. And yet Mr. 

 Cope writes from the other side of the Atlantic to assert that 

 there is no possible cause of departure from parental type 

 in offspring, excepting that assumed in Lamarck's unproved, 

 improbable speculation ! E, Ray Lankester. 



December 7. 



Protective Coloration of Eggs. 



Some years ago an idea similar to that of your correspondent, 

 Mr. Grensted (November 21, p. 53), occurred to me, as regards 

 the protective coloration of eggs ; and, curiously enough, the 

 red-backed shrike was one of the birds whose eggs I selected 

 for special observation. My experience has been that the grou.id 

 colour of these eg^^s is quite arbitrary. I fear that I cannot 

 furnish data, as I ought ; but I well remember that I found in 

 Sussex a rather abnormally pale clutch of eggs in a very dark 

 nest ; and that I regarded this, at the time, as completely doing 

 away with my hypothesis. The evidence that I got from other, 

 less striking instances, told about equally for and against. 



Another egg, whose variations I watched pretty closely, was 

 that of the yellowhammer. Apart from differences of marking, 

 the ground-colour of this egg varies from pure or pinkish- white, 

 to a white rather deeply suffused with purplish-red or olive- 

 brown. But in this case, again, the correspondence of colour 

 between the egg and its surroundings could not be made out at 

 all satisfactorily. 



A pale and little-marked specimen of the egg of the spotted 

 flycatcher, that was brought in to me one spring at Malvern, 

 suggested to me that it wouhl be worth while to observe the 

 variations here also. But I again failed to arrive at any con- 

 clusion. 



