Jan. 9, 1890] 



NATURE 



227 



classical termination, become monosyllabic, such as "thallus, " 

 "sorus," "hypha," and "ascus," just as we still speak of a 

 "corolla," a "stigma," a "hilum,"and a "raphe," But, with 

 regard to the great majority of terms in current use in descriptive 

 cryptogamic botany, we entertain not the smallest doubt that the 

 change will gradually be brought about which has, within the last 

 forty years, become established in phanerogamic botany ; and we 

 would venture to suggest to our fellow- workers in cryptogamic 

 botany in this country and in America, whether it will not be 

 best to accept it frankly once for all. 



Alfred W. Bennett. 



Exact Thermometry. 



I AM quite in agreement with Prof. Sydney Young (NATURE, 

 December 19, p. 152), that after the lapse of a sufficient time — 

 let us say, an infinite time — the constant slow rise of the zero- 

 point of a thermometer at the ordinary temperature will attain a 

 definite limit ; but I cannot accept his view that the effect of 

 heating the thermometer to a high temperature is simply to 

 increase the rate at which this final state is approached. If the 

 results of experiment at the ordinary temperature be expressed 

 in a mathematical formula which admits of making the time 

 infinite, the limiting value of the rise (on that condition) will 

 not exceed on the average 2° C, even in a thermometer of lead 

 glass. After exposure to a high temperature, and in the same 

 thermometer, so great an ascent as 18° C. is a possible measure- 

 ment, actually realized. The two phenomena are therefore very 

 diflferent in their nature. 



The view that, owing to the more rapid cooling of the outer 

 parts of the bulb after it has been blown, the inner parts are in a 

 state of tension, and that it is the gradual equalization of the 

 tension throughout the glass that causes the contraction, has 

 frequently been held, and will probably be for a long time the 

 favourite hypothesis upon the subject. It breaks down, however, 

 when we attempt to calculate what the amount of the contraction 

 might be, on the supposition that it is well founded : only a very 

 small portion of the contraction could be thus accounted for. 

 I regret that I cannot now conveniently refer to Guillaume's 

 interesting demonstration of this result. 



Prof. Young has placed on record an experiment with three 

 thermometers, which he heated to 280° C. The zero movement, 

 however, only ranged from 1° to i°-2, — small readings which 

 might very possibly have been obtained, or not, on either of the 

 thermometers at other times. It is consequently very difficult to 

 draw any inference from this experiment. I may, however, 

 mention that closed thermometers made of lead glass are very 

 apt to show a rise of zero after heating to about 120° C. and 

 upwards to some temperature in the neighbourhood of 270° C, 

 and after that a descent of zero ; the temperature of 280° C. 

 would in that case be an unsatisfactory one for a test experiment, 

 and the efi'ect of plasticity might very possibly be masked. On 

 the other hand, if the three thermometers were of hard glass, all 

 the zero movements would in that case be greatly diminished, 

 and the results would be in less bold relief. 



I do not know any substance more curious or interesting in its 

 properties than glass ; and I should be glad if Prof. Young — 

 into whose able hands the matter has fallen — could decisively 

 test my suggestion that plasticity is the main cause of the zero 

 ascent after 120° C. Probably it has little or nothing to do with 

 the ascent at the ordinary temperature. It is, however, known 

 that fine threads of glass are undoubtedly plastic at the ordinary 

 temperature. Edmund J. Mills. 



Melrose, N.B., December 29, 1889. 



THE PAL^ONTOLOGICAL EVIDENCE FOR 

 THE TRANSMISSION OF ACQUIRED 

 CHARACTERS.^ 



TV/rUCH of the evidence brought forward in France 

 "'■*-*■ and Germany in support of the transmission of 

 acquired characters, which has been so ably criticized in 



. ' ."^'^'^ article is an informal reply to the position taken by Prof. Weismann 

 m his essays upon heredity. I have borrowed freely from the materials of 

 Cope, Ryder, and others, without thinking it necessary to give acknowledg- 

 ment in each case. 



Weismann's recent essays, is of a very different order 

 from that forming the main position of the so-called 

 Neo-Lamarckians in America. It is true that most 

 American zoologists, somewhat upon Semper's lines, 

 have supported the theory of the direct action of environ- 

 ment, always assuming, however, the question of trans- 

 mission. But Cope, the able if somewhat extreme 

 advocate of these views, with Hyatt, Ryder, Brooks, Dall, 

 and others, holding that the survival of the fittest is now 

 amply demonstrated, submit that, in our present need of 

 an explanation of the origin of the fittest, the principle 

 of selection is inadequate, and have brought forward and 

 discussed the evidence for the inherited modifications 

 produced by reactions in the organism itself — in other 

 words, the indirect action of environment. The supposed 

 arguments from pathology and mutilations have not been 

 considered at all : these would involve the immediate 

 inheritance of characters impressed upon the organism and 

 not springing from internal reactions, and thus differ both 

 in the element of time and in their essential principle from 

 the above. As the selection principle is allowed all that 

 Darwin claimed for it in his later writings, this school 

 stands for Lamarckism plus — not versus — Darwinism, as 

 Lankester has recently put it. There is naturally a 

 diversity of opinion as to how far each of these principles 

 is operative, not that they conflict. 



The following views are adopted from those held by 

 Cope and others, so far as they conform to my own 

 observations and apply to the class of variations which 

 come within the range of palseontological evidence. In 

 the life of the individual, adaptation is increased by local 

 and general metatrophic changes, of necessity correlated, 

 which take place most rapidly in the regions of least 

 perfect adaptation, since here the reactions are greatest ; 

 the main trend of variation is determined by the slow 

 transmission, not of the full increase of adaptation, but of 

 the disposition to adaptive atrophy or hypertrophy at 

 certain points ; the variations thus transmitted are 

 accumulated by the selection of the individuals in which 

 they are most marked and by the extinction of inadaptive 

 varieties or species : selection is thus of the ensemble of 

 new and modified characters. Finally, there is sufficient 

 palceontological and morphological evidence that acquired 

 characters, in the above limited sense, are transmitted. 



In the present state of discussion, everything turns 

 upon the last proposition. While we freely admit that 

 transmission has been generally assumed, a mass of 

 direct evidence for this assumption has nevertheless 

 been accumulating, chiefly in the field of paleontology. 

 This has evidently not reached Prof. Weismann, for 

 no one could show a fairer controversial spirit, when 

 he states repeatedly : " Not a single fact hitherto brought 

 forward can be accepted as proof of the assumption." It 

 is, of course, possible for a number of writers to fall 

 together into a false line of reasoning from certain facts ; 

 it must, however, be pointed out that we are now deciding 

 between two alternatives only, viz. pure selection, and 

 selection //z^j' transmission. 



The distinctive feature of our rich palaeontological evi- 

 dence is that it covers the entire pedigree of variations : 

 we are present not only at but before birth, so to speak. 

 Among many examples, I shall select here only a single 

 illustration from the mammalian series — the evolution of 

 the molar teeth associated with the peculiar evolution of 

 the feet in the horses. The feet, starting with plantigrade 

 bear-like forms, present a continous series of readjustments 

 of the twenty-six original elements to digitigradism which 

 furnish proof sufficient to the Lamarckian. But, as 

 selectionists would explain this complex development and 

 reduction by panmixia and the selection of favourable 

 fortuitous correlations of elements already present, the 

 teeth render us more direct service in this discussion, since 

 they furnish not only the most intricate correlations and 

 readjustments, but the complete history of the addition 



