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Maphtgy JUN 12 1926 SG. B Somer,

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Pees PPR RARS

An Experimental Study of Somatic Modifications and their Reappearance in the Offspring

by

Francis B. Sumner

With 11 figures in text and 3 plates

Sonderabdruck aus dem Archiv fiir Entwicklungsmechanik der Organismen Herausgegeben von Prof. Dr. Dr. Wilh. Roux in Halle a/S.

XXX. (Fest-) Band fiir Prof. Roux U. Teil Herausgegeben von Prof. Dr. W. Gebhardt in Halle a/S.

Ausgegeben am 14. Juni 1910

Leipzig Wilhelm Engelmann 1910 b)

| Das Ness. Archiv fiir Entwicklungsmechanik der Organismen

steht offen jeder Art von exakien Forschungen tiber die ,,Ursachen“ der Entstehung, Erhaltung und Riickbildung der organischen Gestaltungen*).

Bis auf weiteres werden auch kritische Referate und zusammen- fassende Ubersichten tiber ‘andern Orts erschienene Arbeiten gleichen Zieles, sowie Titeliibersichten der beziiglichen Literatur aufgenommen.

Das Archiv erscheint zur Erméglichung rascher Veréffent- lichung in zwanglosen Heften sowohl in bezug auf den Umfang, wie auch auf die Zeit des Erscheinens; mit etwa 40 Druckbogen wird ein Band abgeschlossen.

Die Herren Mitarbeiter erhalten unentgeltlich 40 Sonderdrucke ihrer Arbeiten; eine gréBere Anzahl Sonderdrucke wird bei Voraus-— bestellung gegen Erstattung der Herstellungskosten geliefert unter der Voraussetzung, dafi die Exemplare nicht fiir den Handel be- stimmt sind. Referate, Besprechungen und Autoreferate werden mit # 40.— fiir den Druckbogen nach Ablauf des Bandes honoriert.

Die Zeichnungen der Textfiguren sind im Interesse der rascheren Herstellung womdglich in der zur Wiedergabe durch Zinkitzung geeigneten Weise auszufiihren**). Die Textfiguren sind vom Texte gesondert beizulegen; an den Einfiigungsstellen im Texte sind die Nummern der beziiglichen Figuren anzubringen. Sind die eigentlich fiir den Text bestimmten in linearer bzw. punk- tierter Manier hergestellten Figuren sehr zahlreich, so werden sie besser auf Tafeln beigegeben. Tafeln sind in der Hiéhe dem Format des Archivs anzupassen; fiir jede Tafel ist eine Skizze iiber die Verteilung der einzelnen Figuren beizufiigen.

Die Erklarungen der Tafel- sowie auch der Textfiguren sind auf besonderen Blattern beizufiigen.

Die Einsendung von Manuskripten wird an den Herausgeber erbeten.

Der Herausgeber: Der Verleger: Prof. Dr. Wilh. Roux, Wilhelm Engelmann, Hate a/S. (Deutschland). LEIPzia.

*) Den in nichtdeutscher: in englischer, italienischer oder franzié- sischer Sprache zu druckenden Originalabhandlungen ist eine kurze Zu- sammenfassung der Ergebnisse, sei es in der Sprache des Originals oder in

deutscher Sprache beizufiigen. . **) Dies geschieht in linearer bzw: punktierterZeichnung mit tiefschwarzer Tinte oder Tusche, kann aber leicht auch durch nachtriigliches Uberzeichnen der Bleistiftzeichnung mit der Tuschfeder hergestellt werden. Wer jedoch im Zeichnen mit Feder nicht geiibt ist, kann die einfache Bleistiftzeichnung ein- senden, wonach sie von technischer Seite iiberzeichnet wird. Die Bezeichnungen Buchstaben oder Ziffern) sind blo8 schwach mit Bleistift einzutragen, sofern sie der Autor nicht kalligraphisch herzustellen vermag. Anweisungen fiir die Herstellung wissenschaftlicher Zeichnungen zu Textfiguren mit Aus- fiihrungen tiber die einzelnen Herstellungsarten und Proben derselben stellt die Verlagsbuchhandlung den Herren Mitarbeitern gern unentgeltlich zur Verfiigung.

An Experimental Study of Somatic Modifications and their Reappearance in the Offspring.

By

Francis B. Sumner (Woods Hole, Mass., U.S.A.).

With 11 figures in text and tables XVI—XVILII.

Eingegangen am 3. Marz 1910.

For several years past the present writer has studied the effects of differing temperature conditions upon the growth of the white mouse. In a recent paper') some of these effects have been discussed rather fully. It has there been shown that the length of certain peri- pheral parts of the body (tail, foot and ear) is greater in individuals which have been reared in a warm room than in ones reared in a cold room. As regards the tail, the modification was found to be very striking, the mean length of this organ for the two sets of in- dividuals differing in one experiment by more than 30 per cent. In the case of the foot, the difference was less pronounced, but its real- ity was evident in every experiment. The ear, on the other hand, appeared to respond but feebly to temperature conditions?). From determinations of the quantity of hair in two of these contrasted lots of mice, it was shown to be probable that this likewise was affected by sufficiently great differences of temperature. The extreme labo- riousness of these latter determinations has, however, rendered it im- possible thus far to deal with a sufficiently great number of indivi- duals to satisfy the demands of statistical theory.

1) Journal of Experimental Zoology. August 1909.

2) In my earlier paper, indeed, I expressed doubt as to the significance of such small differences as I did detect in the case of this organ. Further observations have, however, lessened these doubts.

318 Francis B. Sumner

I have already dwelt upon the significant fact that these artifi- cially produced differences are just such as have long been known to distinguish northern from southern races of mammals. This fact »will be taken by some as evidence that these differences in nature are likewise ,ontogenetic’ or acquired independently by each indi- vidual. Conversely, the neo-Lamarckian will perhaps argue — and with equal right — that here we have evidence that natural varieties and species have resulted from the accumulated effects of external conditions, since the reality of such effects has been palpably demon- strated by the present experiments«!). Neither conclusion is of course warranted until we have convincing evidence for or against the trans- missibility of this class of modifications. It has accordingly been my chief motive throughout the course of these experiments to obtain evidence of this sort. And it is the object of the present paper to report such data as I have thus far obtained).

I trust that no apology is necessary for the presentation of re- sults which have been derived from a single generation of offspring, comprizing only a few hundred individuals. I need only point out to the reader that this meagre showing is the fruit of monotonous drudgery*) occupying most of my spare time for over three years, during which period my best energies were unavoidably devoted to a quite different task. Without special facilities (and none were at my disposal) it was obviously impossible to obtain the necessary differ- ences of temperature except during the winter months. If one ex- periment failed, it was necessary to wait until the followimg winter before I conld begin anew. Indeed, it was not until the close of the third winter that I obtained a generation of offspring which fulfilled the requirements of the test4). And unfortunately it was not possible, even in this case, for me to keep these animals long enough for fur- ther breeding. They were all killed at the age of about 31/2 months,

1) Op. cit. p. 152.

2) A preliminary account of these data was published in the American Naturalist. January 1910.

3) Any one who has had experience with animal breeding knows that the mere daily care of several hundred mice requires not a little time, especially when one is unassisted. Even this labor has been trifling, however, in com- parison with that required for the measurements and the subsequent com- putations.

4) I. e., which contained a large enough number of healthy animals born nearly or quite simultaneously.

An Experimental Study of Somatic Modifications etc. 319

and thus the experiment was brought to a close. It is not intended, however that the matter shall rest here.

In order to fairly test the heritability of somatic modifications, individually acquired, the following conditions should, I believe, be realized: 1) We must select for experiment such an organism and such a physical agency that the latter may modify the former without directly influencing the germ-cells. 2) We must discover readily measurable, quantitative changes in the parent generation before we can hope to test the reappearance of such changes in the offspring.

Most of the past experiments in this field have been rendered inconclusive by a failure to conform to the first of these conditions. Thus the congenital effects of temperature and humidity upon insects, which have been described by Sranpruss!), FiscHER2), TowER?) and others, are equally well explained as the result of an immediate mo- dification of the »germ-plasm« by the external stimulus itself. The same is true of the enduring effects of special feeding, cumulative from generation to generation, such as have been described by Picrrr) for Lepidoptera and by Houssay®>) for fowls. Indeed this postulate of a »direct effect upon the germ-plasm« has been freely used by WEISMANN and his followers as a cheap and easy way of disposing of most of the experimental evidence which has been brought forward in favor of the inheritance of acquired characters. But it scarcely seems applicable to any effects which may be found to result from the action of temperature upon a mammal. For differences of ex- ternal temperature, as such, manifestly cannot reach the germ-cells of a warm blooded animal unless during the first few days after birth®).

1) Zur Frage der Gestaltung und Vererbung auf Grund achtundzwanzig- jiihriger Experimente. Leipzig 1902.

2) Allgemeine Zeitschrift fiir Entomologie. 6. 1901. 7. 1902.

- 3) An Investigation of Evolution in Chrysomelid Beetles of the Genus

Leptinotarsa. Carnegie Institution. 1906. p. 320. pl. 30.

4) Mémoires de la Société de Physique et d'Histoire naturelle de Geneve. 35. 1905.

5) Archives de Zoologie Expérimentale et Générale. 4¢ série. VI. 1907.

6) PeMBREY (Journal of Physiology. Vol. XVIII. 1905) found the body temperatures of adult mice to remain constant at widely different external tem- peratures. In the young, however (under ten days old), the internal tempera- ture was found to vary with that of the atmosphere. These experiments should be repeated with the aid of more delicate instruments than ordinary mercurial thermometers. At present it is, of course, open to the Weismannian to contend 1) that very slight differences of internal temperature may actually be produced in the parents and may be responsible for any effect upon the succeeding

320 Francis B. Sumner

As regards the second of the above stated conditions which should be fulfilled by the experimenter, it is obvious that in the present in- stance I have produced readily measurable, quantitative changes in the parent generation. It would appear scarcely necessary to urge that a modification must first be manifested by the parents in order that it may be transmitted to the offspring. Yet we read of one in- vestigator who watched for a reduction in the size of the wings of flies which had been prevented from flight for more than 40 gen-— erations. It is difficult to understand how the length of an insect’s wing could be increased or decreased by use during the life of the individual; and it is therefore scarcely surprising that such an effect was not found to be cumulative.

If »acquired characters« are in reality transmitted, we should not in a given case expect that more than a small fraction of a par- ental modification would reappear in the first generation of offspring. For this reason it is plain that we have more to hope for from a comparison of averages based upon the measurements of large masses of individuals than from a search for quwaldtative differences of a sort which are apparent to the eye. Yet with a few exceptions, past experimenters in this field have dealt with modifications of color, or of physiological reactions, such as do not lend themselves readily to quantitative treatment. Ever so slight measurable changes, if suffi- ciently constant, would be of far greater significance than occasional manifestations, however striking; for the latter are always open to the interpretation of being »mutations«<, examples of »reversion« or the like, which are purely accidental as regards the conditions of the experiment.

Having discovered suitable modifications in the parent genera- tion, there are theoretically two methods by which we may attack the problem in hand. We may either 1) raise the offspring of the experimental and control‘) lots under identical conditions, or 2) we may raise the offspring of the modified parents under the same con- ditions as were employed to effect the original modifications. In the first case, we should compare the two sets of animals having differ-

generation; or 2) that in any case the germ-plasm may be influenced during those early days of life before the animal has become strictly homoiothermice.

1) For the sake of simplicity I have here assumed that one-lot was merely a >control« lot, i.e. one exposed to normal or indifferent conditions. In my own experiments, however, I have chosen conditions with a view to modifying both sets of individuals in opposite directions. _ |

An Experimental Study of Somatic Modifications ete. 321

ent parentage. Assuming a given modification of the value x, and supposing that o represents the proportional part of this to be trans- mitted, the offspring of the two lots would be found to differ by the quantity =. If the second of these methods were employed, we

should compare the second generation with the parent generation, the two being measured at the same age. Assuming as before that the parents had been modified to the extent x, the offspring, according

| to hypothesis, would be found to be modified to the extent 2 + —,

i. e., the effect of the conditions would have been cumulative.

Now,: as a matter of fact, I have attempted both of these tests upon rather a large scale; but I have not yet found the second one to be practicable, owing to the difficulty, without special facilities, of repeating precisely the same temperature conditions during the lives of two successive generations!). But, the first of these tests finally proved to be practicable, and has yielded the results which are dealt with on the ensuing pages.

The methods which I have employed in dealing with the parent mice have been described in detail in my paper of 1909, so that little attention need be devoted to them at present. The parent generation (i. e. that immediately subjected to the experimental conditions) which is here to be considered is the one which I have discussed on pp. 139—144 of the paper cited, under the heading »Series of 1908—1909<«. At the date of writing that account, however, these mice had not yet reached maturity. The temperature conditions to which they were subjected from the commencement of life?) until some days before the birth of their last brood of offspring are represented in Fig. 1 of the present paper. The mean temperatures?) of the warm and cold rooms respectively throughout this entire period were 21.27° and 5.57° C. respectively. For the period prior to the date of pairing (May 2), the mean difference was somewhat greater than this, viz. 16.8° C. Since the curves shown in the chart are based upon weekly averages, the extremes of temperature are of course eliminated. The

1) See foot-note on p. 324 and 325 below. 2) Sometimes commencing with the day of birth, sometimes a few days after this, in many cases before birth i. e. during the pregnancy of the mother. 3) 1 am indebted to my wife for the tedious work of compiling these data from the thermograph sheets. Archiv f. Entwicklungsmechanik. XXX. 2. oT

Francis B. Sumner

322

average daily range was 11.2° for the warm room and 6.2° for the

cold room. The mean relative humidity, during the first four months

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of the experiment was roughly 40 per cent for the warm room and

75 per cent for the cold room. This factor, as well as temperature

An Experimental Study of Somatic Modifications etc. 323

proper, may therefore have played a part in the results produced. For present purposes, however, it matters little whether one or both of these factors was concerned.

Each entire brood of mice with its mother'), was transferred as soon as it was received from the dealer to one or the other of these experimental rooms. No selection was exercised in thus disposing of the mice, the broods being chosen at random”).

In all 98 mice, representing 22 broods, survived to the age of 42 days in the warm room; 88 mice, representing 23 broods sur- viving to this age in the cold room. During the ensuing months there were, aS commonly happens, a considerable number of deaths. At the time of the final pairing (May 2) 39 warm-room females and 34 cold- room females were still living. The males, with the exception of those which were selected for breeding purposes*), had previously been killed.

The following table from my early work (1909, p. 138) summarizes the results of the measurements made upon these mice at the age of six weeks. The diagram (Fig. 2) shows the differences in tail length between the warm-room and cold-room individuals (both sexes), these being divided into groups according to weight.

Series of 1908—1909 (parents): Weight and tail length at six weeks.

| 12.604 | 13.180 12.663 11.889] 67.19) 60.11) 68.95) 59.49 i 0.238 | 0.241 + 0.217 + 0.195 |= 0.55 |= 0.51 | 0.48 | + 0.53

| | Standard de- | 3.119) 2.522; 2.107) 1.783; 598) 5.20) 4.61 4.63 viation = 0.201 |= 0.170 = 0.153 ist 0.138 |=— 0.39 |=— 0.36 | 0.34 | + 0.37

)

1) In a large proportion of cases before birth (see above).

2) It would doubtless have been a somewhat more scientific method of procedure to divide each litter into two portions, for the warm and cold rooms respectively, thus ensuring the presence, in these two rooms, of mice having the same parentage. This indeed had been done in the series of the preceding year, but such a procedure naturally involved considerable difficulties. I have therefore acted upon the supposition that the use of a sufficiently large number of broods would minimize the possibility that the two contrasted lots differed appreciably in their mean hereditary constitution.

3) The principle of selection was as follows: that male was chosen from

21*

324 Francis B. Sumner

Unfortunately, only the weight and tail length of these mice were determined at the age of 6 weeks. At this time I did not realize that the foot and ear of a living mouse might readily be measured if the latter were etherized. The modification of foot-length and (with less certainty) of ear-length has already been demonstrated, however, for other lots of mice. Moreover, in the case of one set, comprizing over two hundred individuals, foot and ear measurements were made at the age of six weeks. The results of these latter measurements have

77 76 75 74 73 72 71 70 C 69 pee 67 66 65 64 63 62 64 60 59 58 57 56 55 . $° 9 10 41 42 18 #4% #45 “46 “47 '48 °OxS)) See

Curves showing tail length of parent mice at the age of 42 days. The upper line (W) represents the

condition in the warm-room animals; the lower line (C) representing the condition in the cold-room

animals. Abscissas denote weight in grams; ordinates denote tail length in millimeters. The figures along the curves represent the number of individuals in each size-group.

been plotted in graphic form (Figs. 3 and 4)1) and will be of interest by way of comparison with the curves (Figs. 6 and 7) which have

each brood which in weight approached most nearly the mean of the entire lot (»>warm« or »cold<«). Each male used for breeding was derived from a different brood.

1) This lot of mice comprized 80 cold-room and 129 warm-room individuals. They were the first offspring of the same parent brood as that just referred to, i. e. the parents of the generation to be discussed below. Since they were likewise subjected to considerable temperature differences, a possible cumula-

An Experimental Study of Somatic Modifications etc. 325

been constructed for the later offspring of the same parents. These latter curves are based upon measurements made at the same age (6 weeks), but they do not, like the foregoing, represent differences produced during the induvidual lifetime.

The relative modifiability of tail, foot and ear are clearly shown in the present diagrams (3 and 4), though it must be borne in mind

Fig. De 1 82

7 8 Pee diem te) 13 14 AS 16.47 18 ~-49 20° 27 (22

Curves representing tail length, at 42 days, of another lot of mice (first offspring of those represented in Fig. 2), which have been subjected to similar differences of temperature. For further explanation, see preceding figure.

that the scale for the two last characters is five times as great as that for the tail.

tive effect was sought for. Reference to the temperature chart (Fig. 1) shows us, however, that after the middle of March, when these second-generation mice were born, the temperature differences between the two rooms diminished rapidly. Thus the offspring were subjected to decidedly smaller differences than were the parents; and under these circumstances we could hardly hope to discover any cumulative effect. As a matter of fact, the figures, though in- conclusive, are favorable, rather than contradictory, to the hypothesis of trans- mission. They will not, however, be presented here.

326 Francis B. Sumner

The parent mice, after they had been exposed to these temperature extremes for about six months, were paired for a second time on May 2, 1909. The resulting offspring are those to which attention will henceforth be devoted in this paper.

The demands of our problem would have been realized more

Fig. 4.

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7 8 S40, 11 12 :13 44 15 16 47 483. 4930 eee

Foot and ear length of same mice as those represented in Fig. 3. Note that the vertical scale is five times as great as in the preceding figure.

completely had the two contrasted sets of parent mice been transferred to acommon room before pairing. Unfortunately this was not done’). Indeed the females were not removed to such a room until each was

1) My failure to do so was the result of deliberate intention. At the time of pairing this lot, I had in hand another lot of modified individuals which I expected to pair later under temperature conditions which should be identical for the two sets of parents. I should thus be able to perform both of these experiments, and further restrict the possibilities of interpretation. Cireum- stances prevented the fulfilment of this plan.

An Experimental Study of Somatic Modifications ete. 327

discovered to be pregnant. The discovery was made, on the average, about five days before the birth of the young, i. e. about two weeks after the actual commencement of pregnancy. Thus some indirect influence of the external temperature conditions upon the developing fetus is at least conceivable. Such a possibility will be considered later. At present I shall merely point out that at the time of the pairing (May 2) the differences in temperature between the two rooms had diminished greatly (Fig. 1) and that they continued to diminish rapidly. The average difference from May 2 to May 29 (when the last of the parent mice were brought into a common room) was only 7.6° C., as compared with a difference of 16.8° during the preceding period. Furthermore, the mean date of the commencement of pregnancy was not May 2, but some days later.

TBirth ist TMeas. 2d TMeas.

M Jun Jul Auda. Sent. 18 925° 4 1 “9 aa ee 2 9 6” 13 2027 39 40047 24 sP 14

Curve showing temperature conditions to which the offspring of the modified parents were subjected from biith up to the time of the last measurements. For further explanation see Fig. 1.

From the time when pregnancy became apparent, the two sets of mothers were kept in the same room and under conditions which were indentical for all, so far as care could make them so. Unequal temperature conditions were particulary guarded against. The cages containing the two contrasted sets of animals were kept close together upon alternate shelves, and this arrangement was continued throughout the first six weeks of the life of the young.

The temperature conditions to which the offspring were exposed are represented graphically in Fig. 5. The mean temperature for the entire period was 21.4° C. That from the mean date of birth (May 25) to the mean date of the first measurements (July 6) was 20.8°; to the mean date of the second measurements (Sept. 8) it was 21.4°.

In all, about 182 living') mice were born by the warm-room mothers; about 172 by the cold-room mothers. Of these, 141 offspring

') A considerable number of still-born young are always to be reckoned with.

328 Francis B. Sumner

of the warm-room parents, belonging to 33 litters, and 145 offspring of cold-room parents, belonging to 30 litters, survived to the age of six weeks, when the first measurements were made. There was thus a somewhat greater mortality among the warm-room descendants, a tendency which was manifested even more strongly during the sub- sequent history of the animals.

Since the atmosphere in which these mice were reared underwent considerable changes of temperature from day to day and from week to week, depending upon climatic conditions, it was of course important that the animals should commence their lives at nearly or quite the same time, in order that they might all be subjected to conditions as nearly identical as possible throughout their history.

It is fortunate, therefore, that the mean date of birth differed in the two contrasted lots by only half a day. The extreme dates were May 21 and June 6 for the cold-room descendants, and May 22 and June 7 for the warm-room descendants. Furthermore, nearly 80 per cent of the former lot were born within a period of 5 days (May 21 to 25, inclusive); while 85 per cent of the latter lot were born within an equal interval (May 22 to 26, inclusive). Thus it will be impossible to ascribe any constant differences which may be discovered between these two lots of mice to differences in the external conditions to which they had been subjected during their own lifetime.

The young were measured first at the age of 42 days!). In order that the ear and foot length might be measured accurately at this time, the mice were rendered insensible by ether. The linear meas- urements were taken with a graduated sliding caliper, indicating tenths of a millimeter. In the case of the foot and ear, two meas- urements were made of each, the mean figure being employed in the computations?). The caliper scale was at all times invisible to me until the instrument was finally adjusted. This practice of course diminished the chances of unconscious bias in making the measure- ments. Further precautions were taken at the time of making the second series of determinations at the age of 3!/, months (see below).

1) In a small proportion of each lot the age was 43 days; in a yet smaller number it was 41 days.

2) The average difference between the first and second reading of the caliper was 0.19 mm for the foot and 0.12 mm for the ear. Assuming that the value sought for lay between the two readings of the instrument, it will be seen that the average error for foot and ear equals in each case about half the mean difference which was found to obtain between the two contrasted lots of mice.

An Experimental Study of Somatic Modifications etc. 329

From this earlier series of measurements the following gross averages were obtained: Weight Tail Foot Kar

(grams) (mm) (mm) (mm) Cold-room descendants . . . . 10.897 71.04 17.833 12.434 Warm-room descendants .. . 10.631 71.19 17.960 12.536

It will be seen at once that, although the offspring of the warm- room mice average slightly less in weight, they have slightly longer tails, feet and ears than the offspring of the cold-room mice. These differences are exactly such as were noted, on a larger scale, in the parent generation. But such gross averages do not, in themselves mean very much. In each of the contrasted lots were comprized individuals of widely different size (the extremes were 6.5 and 19.3 grams). Our material, therefore is not at all homogeneous.

Accordingly I have divided the animals into groups, each com- prising individuals of approximately the same weight. These groups have further been subdivided according to sex, the averages for the males and the females being determined separately. Herewith are appended in tabular form the results of such an analysis (Table A).

Considering first the averages for the two contrasted sets of individuals within each size group as a whole (i. e. the sexes being combined), it will be seen that there are 11 groups in which such a comparison between warm-room and cold-room descendants is possible. The mean tail length for the former animals is greater in eight of these eleven cases (exceptions starred); the mean foot length is greater in nine of the eleven cases; while the mean ear length is greater in nine cases and equal in one case. Let us consider the likelihood that such results have been obtained through »chance<, i. e. that they are the result of a multitude of independent causes having no relation to the conditions of the experiment.

Our method of procedure is the same as that employed in deter- mining the probability that a given number of »heads« or »tails« shall be thrown in the course of tossing a coin‘). We here resort to the well-known formula of the binomial theorem: (a@-+ b)” =a” +

na’! b+ eal an—2 62 + eae lar sales ae ee ete.

1) Apology is perhaps due for this excursion unto elementary mathematics. It is safe to say, however, that most of us allow our knowledge of even such elementary principles as these to lapse through years of disuse.

330 Francis B. Sumner

Now in any given throw, the chance for either a »head« or 3 »tail« is of course 1 out of 2. Our binomial thus becomes

1 1 \x G +3)

This, upon expansion and simplification, resolves it self into:

(2) 4 (Lt mitt (1) wll m8) ig

As a concrete illustration, suppose that the number of throws (2) = 4, then our equation becomes:

2A Ne ee (EG eee aE (+a) =rettetietietie The successive coefficients (1, 4, 6, 4 and 1) represent respectively the chances that we shall throw 4 heads, 3 heads + 1 tail, 2 heads + 2 tails, 1 head + 3 tails, and 4 tails’).

If, instead of 4 trials, we should take 11 trials, the chances of our throwing heads every time would be 1 in 2048; the chances of throwing 10 heads and 1 tail would be 11 in 2048; those of throwing 9 heads and 2 tails would be 55 in 2048, etc. What, now, are the chances that we shall obtain as large a proportion of heads as 9 out of 11? To find this we determine the collective chances for 11,

1+ 11+ 55 67 1 10 and 9 heads, i. e. 5048 » Of SoqQgr OF approximately 30°

The same figure represents the chances that in as large a majority of our size-groups as 9 out of 11 the mean figure for a given character shall be greater in the warm-room descendants.

1!) This may readily be verified by anyone who cares to figure out the number of possible combinations of H and T in four consecutive throws. We have H+H+H+H, H+H+H+T, ete. ete. It will be found that 16 such. combinations are possible.

An Experimental Study of Somatic Modifications ete. 331

A table has been prepared (preceding page) showing the like- lihood of the »accidental« occurrence of such majorities for each of the characters singly and for all of them combined‘). It will be seen that the cumulative improbability of the occurrence of all these majorities in the same direction is very high indeed, being about one in 2,400 in the case of the figures for the sexes combined. When we consider the sex-groups separately, it will be seen that the chances for the purely »accidental« occurrence of such majori- ties are even slighter. Those for the preponderance of the »warm« figure in 43 cases out of 57 (with one case of equality) are but a little over one in 20,000.

It must here be granted that those figures which express the cumulative improbability of a similar preponderance being manifested in all three of the characters measured are subject to one important qualification. They are accurate only upon the assumption that these characters vary quite independently of one another. In reality, there is probably a certain degree of correlation, the extent of which has not been determined. This correlation would, of course, considerably increase the chances here stated. But in any case they would remain so slight that in most of the practical affairs of life we should reject them as not worth considering.

The fact is worth noting that it is among the females that the preponderance of the »warm« over the »cold« figures is shown with the greatest approach to unanimity. For example we find among the 57 pairs of figures which admit of a comparison between two averages for the same sex, the following distribution of cases:

1) It will be found that these figures differ throughout from those given in my preliminary paper in the American Naturalist (Jan. 1910). In most cases the probabilities here stated are just half as great as those which I had previ- ously allowed. My earlier figures indicated the probabilities for the occurrence of such majorities in ecther direction. We are, however, only concerned with the probabilities for a preponderance in one direction, i. e. in favor of the warm- room descendants.

Another source of discrepancy between the present figures and the earlier ones results from the treatment of those cases in which the two averages for a given character are equal. In the present computations, I have divided each instance of equality between the plus and minus groups. For example, to take the case of the ear measurements in the accompanying table (first-part), I have regarded the >»warm< figure as being larger in 91/5 of the size-groups, smaller in 11/2 of these. The probability given is the mean of the figures for 9 out of 11 and 10 out of 11. This seems a fairer procedure than that of throwing the ease of equality out of consideration as I had earlier done.

332 Francis B. Sumner

>Warm« figure >»Warm< figure The two equal larger smaller OC ae eee 21 9 0 Femaies. 9... < ) a 4 1

The same difference between the sexes in this respect is shown even more forcibly by the figures derived from the later measure- ments.

Thus far we have treated these groups as of equal value in our computations. From our table it will be seen, however, that the groups differ greatly in respect to the number of individuals com- prized, and in respect to the magnitude of the differences shown. I have computed the probable errors of the averages for those seven size-groups which are large enough to make this worth while‘). Tak- ing into account the three characters (tail, foot and ear) for the seven groups, we have, accordingly, twenty-one probable errors for each of the contrasted sets (»warm<« and »cold«). By a little figuring it may be shown that in twelve of these 21 cases the difference between the two contrasted averages is two”) or more times as great as the probable error of that difference; in one case the difference is over three times its probable error, and in three cases it is over four times its probable error. Furthermore, it is important to note that in none of the exceptional cases (i. e. those in which the cold-room descendants have longer peripheral parts) is the difference between the averages as high as two times its probable error*). The signifi- cance of these facts will be appreciated by anyone familiar with statistical methods.

Diagrams (Figures 6 and 7) have been constructed permitting of a comparison between the two contrasted sets of mice, with res- pect to the mean length of tail, foot and ear, for each of the size groups. The insignificance of the differences in the exceptional groups as compared with those conforming to the rule, is still further em- phasized by these diagrams.

The question naturally arises: How do these differences between the warm-room and cold-room descendants compare in amount with the differences which were shown by the parents as a direct result of the

1) I. e. those in which both sets (»>warm« and »cold<) consist of ten or more individuals apiece (in one exceptional case, one set contains only nine).

2) Here including one case in which it was very nearly twice as great.

3) In one case it is practically equal, in another it is considerably less.

An Experimental Study of Somatic Modifications ete. 333

external conditions to which they had been subjected? Unfortunately, the data necessary for a satisfactory answer to this question are not at hand, since, in the case of the parents of this particular lot, only the weight and tail length were determined at the age of six weeks'). We may, however, make this comparison in respect to tail length.

Fig. 6.

6 4 8 meeameit 12) 13) 44 45° 46.47 48.49

Curves showing tail length, at 42 days, of the offspring of modified parents, reared under conditions

identical for all. The heavy line(W) represents the condition in the offspring of warm-room parents,

the lighter line (C) representing the condition in the offspring of cold-room parents. Abscissas denote

weigth in grams; ordinates denote tail length in millimeters. The figures along the curves denote the number of individuals in each size-group.

An inspection of Figures 2 and 6 shows at once that this difference has very much diminished in the second generation.

It will likewise be instructive to compare the the mean differ- ences shown by parents and offspring in respect to this character.

1) See above.

334 Francis B. Sumner

To determine the extent of these differences, we shall consider, not the differences between the gross averages, for reasons already stated, but the average difference between the »warm«< and the »cold« figure within each size-group. The mean difference in tail length, as thus computed, shown by the parent generation at the age of six weeks, was 8.195 mm, that shown by the offspring being 1.264. Thus the latter figure is a little over 15 per cent of the former.

Fig. 7.

COM BWHUSCNMLSHX WE RUE N@WEOmNEDUSGN

ao avo

~ e

-~ ¥ by Bese roekuUutuxyecen

~

6 7 ds) ae? Anse Ae iGoe aa 1S 16 47> "4s

Showing foot and ear length of same mice as those represented in Fig.6. Note that vertical scale is five times as great as in preceding figure. For further explanation, see the latter.

As regards foot and ear length, we may profitably compare the generation with which we are dealing here with the first offspring of the same parents. These first offspring, it will be recalled, were subjected to temperature differences similar to (though not as great as) those to which the parents had been exposed. An instructive com- parison may therefore be made between the curves (Figs. 3 and 4) for these mice which had themselves been directly modified and

An Experimental Study of Somatic Modifications etc. 335

the curves (Figs. 6 and 7) for mice whose parents alone had been modified.

We may likewise compare the figures expressing the mean differences, computed according to the principle just stated:

Mice directly Offspring of modified modified *) individuals Pee 9.710 1.264 a 0.7138 0.1890 wae me. 0.2021 0.1281

Comparing these two sets of figures, we find that the difference in tail length is 13 per cent as great in the second case as in the first; the difference in foot-length is 26 per cent as great, while the difference in ear length is 63 per cent as great! These figures are not offered as expressing, with even a rough degree of approxi- mation, the proportional part of these parental modifications which is handed on to the offspring — even granting that it is handed on in any strict sense of the words. The relative magnitude of the three percentages is particularly surprising, in view of the fact that the tail is the organ which responds most decidedly to the tem- perature differences, while the ear has been shown to be the least affected. It might be argued that the very plasticity of a part, which makes it so responsive to outside influences, might render it corre- spondingly ill-adapted to retaining such impressions permanently). Such speculations would be decidedly premature, however.

As already stated another set of measurements was made with this same lot of mice when they reached the age of about 3!/. months. By that time the numbers had been considerably reduced by death®).

1) Comment may be made in passing upon the fact that in this lot the difference in tail-length is over 1.5mm greater than in the case of the parents, despite the fact that the temperature differences had been much greater for the latter. I will not lay much emphasis on this circumstance, however, since it has been shown in my earlier paper (1909) that different lots of mice may respond to a very different extent to substantially the same differences of tem- perature.

2) It may be pertinent to point out, likewise, that the tail is far more variable than either the foot or the ear.

3) A certain proportion had succumbed under the influence of the ether. at the time of the 42-day measurements. Commencing with about July 1, I ‘was prevented by other duties from giving proper attention to the animals. They were kept in a limited number of cages, and over-crowding was doubt- less responsible for many deaths.

336 Francis B. Sumner

There were at the later date 114 of the cold-room descendants, and only 84 of the warm-room descendants. The survivors all appeared to be in good health, however, and few or no deaths had occurred during the few weeks immediately preceding these measurements.

At the time of the first series of measurements, each mouse had been measured upon arriving at a certain age (42 days). The later series, on the contrary, were made during a period of one week Septem- ber D—11), and without reference to the age of the individual mice‘). An approximately equal proportion of warm-room and cold-room des- cendants were, however, measured each day of this period. It was deter- mined later that the mean age of the two sets of individuals at the time of these second measurements was in each case almost exactly the same, i. e. about 105 days. The youngest mouse was 90 days old, the oldest being 113 days old. These extremes were exceptional, however, for 76 per cent of the cold-room descendants were between the ages of 103 and 110 days, while 87 per cent of the warm-room descendants were between the ages of 103 and 109 days.

In order to exclude the possible influence of suggestion or un- conscious bias in determining these rather delicate caliper measure- ments, I adopted at this time the plan of keeping myself in igno- rance as to the parentage of each mouse until the latter had been measured. The animals were put into separate small cages, each bearing an identification mark upon the bottom. These cages were then »shuffled« by one of my colleagues in the laboratory.

The mice were killed at the time of these latter measurements. For this reason it was possible to determine another character — body length — with accuracy. This is not feasible with living ani- mals, even when etherized.

The gross averages for the two contrasted sets of individuals are presented herewith:

Weight Body length Tail Foot Ear Cold-room descendants 18.56 86.703 81.162 17.8960 13.3386 (114) Warm-room descendants 19.45 87.683 82.732 18.1427 13.5143 (84)

1) The latter — identified by marks, to be sure — had been mingled | together in a few large cages, and it would have required much labor to pick out, each day, those which had arrived at the age desired.

An Experimental Study of Somatic Modifications ete. 337

It will be seen at a glance that the mean length of tail, foot and ear is, aS was previously the case, greater for the warm-room descendants than for the cold-room descendants. But the differences between these gross averages signify even less here than in the case of the earlier figures, since the two contrasted lots now differ quite appreciably in their mean size. The warm-room descendants are heavier on the average by more than a gram, while their average body length is nearly one millimeter greater. For this reason it is even more important that our animals should be divided into groups according to size. I have, accordingly, grouped the mice in two dif- ferent ways: 1) according to weight, as was done previously, and 2) according to body length. The latter method of grouping seems a much fairer one than the first, for it seems likely that the length of the appendages is correlated primarily with body length and only incidentally with weight. The latter, of course, depends in large degree upon the nutritive condition of the animal, amount of adipose tissue, etc. The single weight-groups, it may be added, contained individuals which differed from one another by as much as 4 or 5mm of body length.

To consider the second of these methods first, the animals were divided into groups, within each of which the individuals differed by less than one millimeter in length. The appended table (B) permits of a comparison of warm-room and cold-room descendants within each of these size-groups, for each sex separately, and for the two sexes combined.

Considering the averages for the two sexes combined, we find that in the 15 size-groups which admit of such a comparison, the »warm« figures for tail, foot and ear length are larger than the »cold« figures in 12, 11 and 10 cases respectively. The chances for the accidental occurrence of such majorities are approximately 1 in 57, 1in 17, and 1in 7, respectively. But we have the cumulative testi- mony of all three of these characters, pointing in the same direction. The chances that the »warm« figure shall thus be greater in 33 out of the 45 cases are only 1 in 814).

If we deal with the sexes separately, we find 21 groups within which comparison is possible between the warm-room and cold-room descendants, or 63 pairs of averages, when the three characters are considered. In 40 of these the »warm« figure is larger than the

1) Leaving out of account correlation between these characters (see above). Archiv f. Entwicklungsmechanik. XXX. 2. 292

Francis B. Sumner

338

‘9g “SIg 008 ‘nonvar[dxe roq,ANJ 10g ‘SAOJOUNTT[VL ul YBSUET 1%} OJOUOP SazVUIpsO ‘sLOJOUT[[IM ur qISuUe] Apo ojouep sesstosqy ‘qyduUeT Apoq 0} Surproooe sdno1r8 ozur poepratp e10q ‘syyuom 2/;¢ Jo oS oy} 4e poernsvom ‘SuroSer0y oy} sv Zudsyo Jo UOMTAeUes eMIES Jo YySUET [Ivy,

eee eee ne oO Ge hh FE BR BS ULE! 96 es: es ia ce. PS DS Gd ate by oy tL = é

ZL abet

EL “* GL SL OE 1 RL 62 08 18 28

‘9 “Sly

»cold« figure; in 22 cases it is smaller, while in a single case the

The probabilities for such a state of affairs

two figures are equal.

The author does not

at present care to devote himself further to this pastime.

may be computed by the reader if he chooses.

As was

An Experimental Study of Somatic Modifications etc. 339

W 98

4 Ci 97

i 1 to —~ I, aD a hi : he 2 { td = | > e cs =| be 5 = = = bp om Do i») —_— SS >) o ™ a =] a a = 3 ie WR —) = a> on Ce ° 2) iP) ioe) 50 3 o oo S 2 YY >) co " ® S3 La 2 aD = z wad 2 <> Bes = 2 8p a — _ = 2 og i) Cet st ° oo - ra) re ioe) 8 Lal i) o S 5) an! toy) Dn >) =) 3 n nd Set 9 ° ~ a = Sp jes) Lees | ] ® Lil = I {o> 3 is im Sr ] Ss I i= 1 Lees 3 t | » { ‘eek 3 { 1 ee | | i { im ' ! oO! N 1 io a eS 1 a 4 CHE RAK PmOKOHeE RA KH SAOHOHL MACS Aonoestaanroanse & 2 = = 2s

the case with the earlier measurements, the females show a much

closer approach to unanimity in this tendency than the males. Among

the former there are 19 positive cases and 8 negative ones; among 22*

340 Francis B. Sumner

the latter, 21 positive cases, 14 negative ones, and 1 case of equality.

The diagrams (Figs. 8 and 9) show these relations graphically, and demand no discussion. As regards the ear, the case can hardly be regarded as convincing.

In the next table (C) the averages for the weight-groups have been presented. In the 12 groups which admit of a comparison between

Fig. 10.

Hi 42 «6 130—CO 14 45 0COG 7 618: «6990 282428 Pe eee

Tail length of the same generation of offspring, likewise at the age of 31/2 months; here grouped according to weight.

the averages for all individuals (sexes combined), the mean length of tail, foot and ear is larger in the warm-room descendants in 8, 10 and 9 cases respectively. The probabilities for these majorities are 1 in 5, 1 in 52 and 1 in 14 respectively. The chances that in 27 out of 36 cases (considering all three characters) the »>warm« figure would be larger are only 1 in 508.

It must be granted, however, that when the sexes are considered separately, the figures are somewhat equivocal. There are 15 groups in which we may compare the »warm« and »cold« figure for mice

An Experimental Study of Somatic Modifications etc. 341

of the same weight and of the same sex. Taking into account the three characters under consideration, there are thus 45 pairs of con- trasted figures to be reckoned with. The figure for the »warm<-room descendants is greater in 26 of these cases, smaller in 19. The pre- ponderance is thus not large. Furthermore, for one character (foot length) there is an actual majority in favour of the cold-room descen- dants, i. e. there are only 7 cases in which the »warm« figure is larger, 8 in which the »cold« figure is larger. Indeed among the males alone, there are only 3 positive cases and 6 negative ones.

Fig. 11.

eNO UHDANF CO* NOL URN BLS#NUEUADH

~ ~~ ~~

&

MOSK NOHKYUAYRWSHN

x

eerie iveee 47 468 49 20 21 22 23. 24 25 26 -27

Foot and ear length of same mice (see legend for Fig. 10).

When all three of the characters are considered, the males show 12 positive cases to 15 negative ones, i.e. the »cold« figures is larger in an actual majority of cases. For the females, however, the rela- tions are quite different. We have 14 positive cases and 4 nega- tive ones.

Thus, a consideration of this last table, taken by itself would not be very convincing, though it must be remembered that the ge- neral tendency of the figures, viewed as a whole, is distinctly in accordance with the results of the earlier analyses. As may be seen

342 Francis B. Sumner

at a glance, the curves (Figure 11) which are based upon the aver- ages for the weight-groupts (sexes combined) show that for foot and. ear length, at least, the same relations obtain as were previously portrayed in Figs. 7 and 9.

It might indeed have been anticipated that the results derived from these later measurements would be less striking than those der- ived from the earlier ones‘). ‘To begin with, the number of indi- viduals was considerably reduced, they varied somewhat in age, and the mean size of the two contrasted lots differed. Then too, we have to reckon with the principle of the »levelling down of initial differ- ences<, concerning which I have had considerable to say in an ear- lier paper. And lastly, it is possible that unconscious bias in the use ‘of the calipers may have somewhat exaggerated the differences shown in the earlier series of measurements, although caution was, of course, _taken to avoid this.

Summary and Conclusions.

1) Mice which were reared in a warm-room (about 21° C.) were found to differ considerably from those reared in a cold-room (about 5° C.) as regards the mean length of the tail, foot and ear. These organs were found to be longer in the former than in the latter set of individuals. (The two sets probably also differed from one another in respect to the amount of hair, though this does not concern us here.)

2) These same differences were found to be manifested by the offspring of the warm-room and the cold-room parents, although the animals belonging to this second generation were all reared together in a common room, and exposed to identical temperature conditions. In the experiment here considered, there were 141 of the warm-room descendants, 145 of the cold-room descendants.

3) These differences between the warm-room and cold-room des- cendants are revealed not only through a comparison of the gross averages for these three characters in the two contrasted sets of in-

1) As a matter of fact, I had not yet analyzed the data from the earlier measurements at the time when the later ones were made, and at that time had no expectation that these interesting relations would be shown to exist. Indeed nothing was observed during the course of the measurements to justify such an expectation.

An Experimental Study of Somatic Modifications ete. 343

dividuals, but by a comparison between averages computed for each group when the mice have been divided into groups according to size, and when these groups have been still further subdivided accor- ding to sex. By calculations of probability it has been shown that the chances for the purely »accidental« occurrence of all these dif- ferences are very slight.

4) These differences among the offspring were manifested with fullest certainty in an earlier series of measurements, made at the age of six weeks. In a later series, made at the mean age of -31, months, the same relations were found to exist, though to a less striking degree.

5) The differences were exhibited with a closer approach to una- nimity by the females than by the males. It does not seem justi- fiable, however, to lay much stress upon this fact without further data.

I will freely grant that this reappearance of the parental dif- ferences in the two sets of offspring is open to a number of interpre- tations. Some of these have little to warrant them and may be dis- posed of briefly:

A. The differences in the offspring may have been due to »co- incidence« or »accident<. The odds against such an occurrence have been shown to be high. Indeed the cumulative improbability that all these differences have been accidental is enormous.

B. They may have resulted unconsciously from a slight though constant biasing of the caliper measurements in favour of that result which was calculated to give the greatest personal satisfaction. This possibility has been excluded in the case of the second series of measurements.

C. Granting their genuineness, these differences may have been due to the immediate effect of temperature as such upon the germ- cells. Since, however, we are dealing with a warm-blooded animal, ' it would be necessary to assume either that such an effect was im- pressed upon the germ-cells during the first few days after birth, before the animal had become homoiothermic, or that slight and hitherto unmeasured differences in the internal temperature of the adults were sufficient to affect the germ-cells. In either case, the produc- tion of parallel modifications in parent and offspring would have to be accounted for.

D. These differences may be related to the circumstance that the difference in temperature conditions to which the parents were sub-

344 Francis B. Sumner

jected was continued (though to a qualified extent) during the earlier stages of pregnancy of the mothers. This interpretation is subject to the same objections as the preceding. It is obvious that in a warm-blooded animal the fetus could not be directly affected by dif- ferences of temperature as such. And, even if we grant some indirect influence upon the fetus, it would be curious indeed if the parental modifications should be so closely paralleled.

Deserving more serious consideration, we believe, are the fol- lowing possible interpretations of these results:

E. The differences may have been due, not to any specific in- fluence (hereditary or otherwise) which has affected the tail, foot or ear directly, but to some general constitutional difference in the off- spring of the two sets of parents. In other words, these differences in the length of the peripheral parts may be correlated with some constitutional difference of a very general sort'). In this connection, it must be admitted that the offspring of the warm-room mice showed a very much higher mortality (40 per cent between the first and se- cond measurements) than those of the cold-room mice (20 per cent). The former were likewise somewhat larger, on the average, when measured at the age of three months. Thus there did appear to exist some sort of a constitutional difference, at least as regards certain individuals. We should not be justified, however, in assuming any such difference in constitution between surviving mice of equal sixe, and these it was which have been compared in our tables. And in any case, we do not thus far have the least evidence that the length of these appendages is correlated with any such congenital differ- ences in constitution.

F. An explanation closely similar to the last would be that the general stage of development in one lot of mice had been accelera- ted or retarded as compared with that of the other. We know that the ears and feet of young mice are relatively much larger than those of older ones. It might be contended, therefore, that the warm-room descendants were in a relatively more juvenile condition, as a result, perhaps, of an enfeeblement to which their parents had been sub- jected. This supposition is hardly in accord, however, with the fact

1) Harar (Journal of Comparative Neurology and Psychology. 1908) be- lieves that he has demonstrated for white rats that underfeeding produces short tailed individuals. Since this conclusion appears to be based upon a consider- ation of only five underfed animals, it cannot be regarded as proven. On the other hand, there is nothing improbable about it.

An Experimental Study of Somatic Modifications etc. 34 5

that these warm-room descendants were no smaller than the cold- room descendants. Indeed they were larger at the time of the second measurements.

G. One of the alternatives considered above (C) might be offered in a modified form. It might be conceded that temperature as such could not affect either the fetus or the germ-cells to any appreciable extent. But it might, on the other hand, be contended that the effects of temperature, even upon the parent body itself, may not be direct, but may be due to the formation of specific chemical substances which, through the medium of the blood, may be supposed to simul- taneously influence the body and the germ-cells. Such a hypothesis ean neither be proved nor disproved in the present state of our knowledge, but it is perhaps the type of explanation which is cal- culated to appeal most strongly to the biologist of to day. It may be pointed out, however, that 27f a mechanism exists whereby the germ- cells may be so influenced as to bring about a modification of the off- spring parallel to that which was undergone by the parent, such a mechanism would be of exactly the same value for evolution as the »tnheritance of acquired characters« wm the old sense. For heredity, however, the case would be somewhat different. We might still continue to talk about the »continuity of the germ-plasm<, though that expression would have been shorn of much of its meaning.

H. Finally, we have the view that the changes undergone by the parent body are themselves registered in some way in the germ-cells, so as to be repeated, in a certain measure, in the body of the off- spring. The »classical< attempt to make this process intelligible is of course Darwin’s hypothesis of »pangenesis«. Other views have been put forward recently‘) which are scarcely to be distinguished from the preceding type of explanation (G).

In conclusion, the writer will express his qualified conviction that the truth is contained in one or both of the last two alternatives. It would not be profitable, however, to enter into any scholastic dis- cussion of these various hypothesis. One after another of these alter- natives must be excluded by carefully planned experiments, and it is the intention of the present writer to continue such experiments on a much greater scale in the near future.

Naples Zoological Station?), Feb. 26, 1910.

1) E. g. the >hormone theory< of CuNNINGHAM (Archiv f. Entw.-Mech. 1908). 2) My hearty thanks are due to the director and staff of the station for facilitating the work of preparing this paper, particularly in placing at my

346 Francis B. Sumner

Zusammenfassung und Folgerungen,

1) Es ergab sich, da8 in einem warmen (etwa 21°C.) Raume aufgezogene Miiuse sich erheblich beztiglich ihrer mittleren Schwanz-, Fu8- und Ohrlinge von den im kalten (ungefiihr 5° C.) erzogenen unterscheiden. Ich fand diese Organe liinger bei dem ersten als bei dem zweiten Tiersatz. (Die zwei Sitze sind voneinander wahrscheinlich auch in bezug auf die Haarmenge unterschie- den, doch geht uns dies hier nichts an.)

2) Ich fand, da®B sich diese selben Unterschiede auch bei den Nachkommen der Warm- und Kaltraumeltern zeigten, obgleich die zu dieser zweiten Gene- ration gehidrigen Tiere alle zusammen in einem gemeinsamen Raume aufgezogen und identischen ‘emperaturverhiltnissen ausgesetzt waren. Bei dem hier be- sprochenen Versuch kamen 141 von den Warmraum- und 145 von den Kalt- raumnachkommen unter Beobachtung.

3) Diese Unterschiede zwischen den Warm- und Kaltraumnachkommen er- geben sich nicht blo8 aus einem Vergleich des groben Durchschnitts der beiden gegensiitzlichen Tiergesellschaften beziiglich der drei erwiihnten Charak- tere, sondern durch einen Vergleich zwischen Durchschnittswerten, die in der Weise fiir jede Gruppe aufgestellt sind, daf die Miiuse erst nach der Gré8e in Gruppen geteilt wurden, und dann diese Gruppen noch weiter in Unterabteilun- gen nach dem Geschlecht. Durch die Wahrscheinlichkeitsrechnung wurde ge- zeigt, da8 die Chancen fiir ein lediglich zufilliges hii aller dieser Unterschiede sehr gering sind.

4) Diese Differenzen unter der Nachkommenschaft zeigten sich mit vollster Sicherheit bei einer friihzeitigen, im Alter von 6 Wochen vorgenommenen Serie von Messungen. Bei einer spiteren, im mittleren Alter von 31/. Monaten an- gestellten Messungsreihe zeigte sich das Bestehen derselben GréSenbeziehungen, doch in einem weniger frappanten Grade.

5) Die Differenzen wurden von den Weibchen mit einer gréSeren Annihe- rung an eine allgemeine Ubereinstimmung zur Schau getragen, als von den Minnchen. Immerhin erscheint es nicht gerechtfertigt, auf diesen Umstand ohne neue Tatsachen zu groBes Gewicht zu legen.

Ich will gern zugeben, da dieses Wiedererscheinen der elterlichen Ver- schiedenheiten zwischen den beiden Nachkommensitzen eine Anzahl verschiedener Erklirungen zuliB8t. Fiir einige von ihnen lassen sich nur wenige Stiitzen fin- den, und diese sollen kurz abgetan werden:

A. Die Verschiedenheiten bei der Nachkommenschaft kénnen auf »Koinzi- denz« oder auf >Zufall« beruhen. Es wurde aber gezeigt, da8 die Wahrschein- lichkeit sehr gegen ein derartiges Vorkommen spricht. In der Tat ergibt sich eine enorme Hiufung der Unwahrscheinlichkeiten gegen die Auffassung, dal alle diese Differenzen rein zufillig sind.

B. Sie kénnten unwissentlich von einer geringen, doch konstanten Beein-

disposal the services of 1 draughtsman, who assisted in the preparation of the charts. The experiments upon which this paper is based were conducted at Woods Hole, partly in the Laboratory of the United States Bureau of Fisheries, partly in the Marine Biological Laboratory. My thanks are due to the director of the latter institution for placing at my disposal a small building in which my >»cold-room« mice were reared during the experiments of the third year.

An Experimental Study of Somatic Modifications etc. 347

flussung der Kalibermessungen im Sinne desjenigen Ergebnisses herriihren, von dem man sich voraussichtlich die grié8te persdnliche Befriedigung versprechen konnte. Diese Méglichkeit ist bei der zweiten Messungsreihe ausgeschlossen worden.

C. Gesteht man ihr wirkliches genuines Vorhandensein zu, so kénnten diese Verschiedenheiten auf dem Einflu&8 der Temperatur unmittelbar als sol- chem auf die Keimzellen beruhen. Da wir es ja aber mit einem warmbliitigen Tier zu tun haben, so miiRte man da notwendigerweise annehmen, dafsi ein solcher EinfluB auf die Keimzellen wihrend der ersten paar Tage nach der Ge- burt ausgeiibt wurde, bevor das Tier noch homéotherm geworden war, oder, daB ganz geringe und bis jetzt noch nicht gemessene Differenzen in der Innen- temperatur der erwachsenen Tiere zur Beeinflussung der Keimzellen hinreichten. In beiden Fiillen wiire fiir die Entstehung paralleler Verinderungen bei Eltern und Nachkommen noch die Erklirung zu finden.

D. Diese Verschiedenheiten kénnten mit dem Umstand in Beziehung ge- bracht werden, daf} die Verschiedenheiten der Temperaturverhiltnisse, denen die Eltern unterlagen, noch wihrend der friihen Schwangerschaft der Miitter anhielten (allerdings in beschrankter Ausdehnung). Diese Erklirung unterliegt denselben Einwiirfen wie die vorige. Es liegt auf der Hand, da bei einem warmbliitigen Tier der Fétus durch Temperaturdifferenzen als solche nicht beeinfluBt werden kann. Und selbst wenn wir einen gewissen indirekten Einfluf auf den Fotus zugeben wollen, so wire es doch sehr merkwiirdig, wenn es dadurch zu so strikten Parallelveranderungen zu den miitterlichen kommen sollte.

Ernstlichere Erwigung verdienen, wie wir glauben, die folgenden Er- klirungsversuche der vorliegenden Ergebnisse:

E. Die Verschiedenheiten kénnen beruhen, nicht auf einer spezifischen Ein- wirkung (durch Erblichkeit oder anderswie), die den Schwanz, den Fu, das Ohr direkt beeinfluft hatte, sondern in einer gewissen allgemeinen konstitu- tionellen Verschiedenheit der Nachkommen aus den zwei elterlichen Tiersitzen. Mit andern Worten: Diese Differenzen in der Liinge der peripheren Teile kiénn- ten im Correlation stehen mit einer gewissen konstitutionellen Verschiedenheit sehr allgemeiner Art!). In diesem Zusammenhange mu zugegeben werden. daB die Nachkommenschaft der Warmraum-Miuse eine sehr viel héhere Morta- litat zeigte (40°/) zwischen der ersten und zweiten Messung), als diejenige der Kaltraum-Miuse (209/)). Die ersteren waren auferdem im Durchschnitt etwas gréBer, als sie im Alter von 3 Monaten gemessen wurden. Also scheint da eine Art von konstitutioneller Verschiedenheit zu existieren, wenigstens soweit das gewisse Individuen angeht. Dennoch waren wir nicht berechtigt, zwischen tiberlebenden Mdusen gleicher Grife irgendeine derartige konstitutionelle Ver- schiedenheit anzunehmen, und nur solche wurden in unseren Tabellen verglichen. Und in jedem Falle haben wir insoweit nicht das geringste Zeichen dafiir, dal die Lange dieser Anhiinge mit irgend solchen congenitalen konstitutionellen Verschiedenheiten in Correlation steht.

1) Harar (Journal of Comparative Neurology and Psychology. 1908) meint fiir die weiBe Ratte gezeigt zu haben, da unzuliingliche Fiitterung Individuen mit kurzen Schwinzen hervorbringt. Da dieser Schlu8 lediglich auf der Be- obachtung von nur fiinf unzuliinglich gefiitterten Tieren zu basieren scheint, so kann er nicht als bewiesen gelten. Anderseits liegt darin aber durchaus nichts unwahrscheinliches.

348 Francis B. Sumner, An Experimental Study of Somatic Modifications ete.

I’. Eine der letzterwihnten ganz iihnliche Erklirung wiirde die sein, daB der allgemeine Entwicklungszustand bei dem einen Miusesatz dem des andern gegeniiber beschleunigt bzw. verzigert worden ist. Wir wissen, daB die Ohren und FiiBe von jungen Miiusen verhiiltnismiGig viel gréBer sind als die von alten. Es kinnte daher behauptet werden, da8 sich die Warmraumnachkommen in einem verhiltnismiSig jugendlicheren Zustande befinden, vielleicht infolge einer Schwiichung, die ihre Eltern erfuhren. Diese Annahme ist jedoch schwer- lich mit der Tatsache in Ubereinstimmung zu bringen, da diese Warmraum- nachkommen nicht kleiner als die Kaltraumnachkommen sind. In der Tat waren sie gréBer zur Zeit der zweiten Messung.

G. Eine von den oben (unter C.) betrachteten Alternativen kinnte sich in veranderter Form darbieten: Man kinnte zugeben, dafsi Temperatur als solche weder den Fiétus noch die Keimzellen irgendwie affizieren kann. Es kénnte aber anderseits behauptet werden, daf die Temperaturwirkungen sogar auf den elterlichen Kérper selbst nicht direkte sein kénnten, sondern auf der Bildung spezifischer chemischer Substanzen beruhen kénnten, welche unter Vermittlung des Blutes gleichzeitig einen Einflu8Z auf den Kérper und die Keimzellen haben kinnten. Eine derartige Hypothese kann beim gegenwiirtigen Stande unsres Wissens weder bewiesen noch widerlegt werden, — das ist aber vielleicht der Erklirungstypus, der darauf berechnet ist, die stirkste Anziehungskraft auf die heutigen Biologen auszutiben. Immerhin soll hervorgehoben werden, daB, wenn ein Mechanismus existiert, durch den die Keimxellen so beeimflupt werden kinnen, daB sie eine Veriinderung der Nachkommenschaft parallel xu den von den Eltern erlittenen Veriinderungen hervorbringen, dieser Mechanismus fiir die Entwicklungs- lehre genau denselben Wert hiitte, wie die »Vererbung erworbener Evgenschaften« vm alten Sinne. Fiir die Erblichkeit wiirde der Fall immerhin etwas anders liegen. Wir kénnten immer noch fortfahren, von der »Kontinuitéit des Keimplasmas< au reden, jedoch wiirde dieser Ausdruck viel von seiner Bedeutung einge- biiBt haben.

H. Endlich haben wir noch die Ansicht, da8 die vom elterlichen K6rper erlittenen Veriinderungen selbst auf irgendeine Weise in den Keimzellen regi- striert werden, so daB sie sich in einem gewissen Grade im Kérper der Nach- kommenschaft wiederholen. Der »klassische<« Versuch, diesen ProzeB dem Ver- stiindnis niiher zu bringen, ist natiirlich Darwins »Pangenesis<-Hypothese. Andre Ansichten sind neuerdings ausgesprochen worden, welche sich kaum von dem vorhergehenden Erklirungstypus (G.) unterscheiden }).

Zum Schlu8 michte Schreiber dieses seiner bedingten Uberzeugung Ausdruck geben, da®8 die Wahrheit in einer oder in beiden von den letzten zwei Alternativen liegt. Es wiirde jedoch nicht viel niitzen, in eine schola- stische Diskussion dieser verschiedenen Hypothesen einzutreten. Eine nach der andern miissen diese Alternativen durch sorgfiltig entworfene Versuche zur Erledigung kommen, und es ist die Absicht des Verfassers, derartige Versuche in nichster Zeit in einem viel gréBeren MaBstabe fortzusetzen.

(Ubersetzt den 7./8. Mirz 1910. W. Gebhardt.)

1) z. B. die »Hormonentheorie« von CuNNINGHAM (Archiv f. Entw.-Mech. 1908).

Archiv fiir Entwicklungsmechanik. Bd. XXX.

T.

able A.

Taf. XVI.

Offspring of Cold-room and Warm-room Parents, measured at 42 days.

Sumoer.

Namber'! Size-group Sex | Parentage | of indi-| Weight Tail Foot Ear viduals 3 Cold ‘ Warm 1_| 6.60 | 60.00 17.100 11.750 Cold 2 | 6.55 | 59.00 16.950 11.900 SOT ee |e || 08 | 61.00 ‘| 16.650* 11.900* Alto-| Cold 2 6.55 | 59.00 16.950 11.900 7 gether! Warm IL 3 6.77 | 60.67 16.800* 11,850* 3 | Lola 3 | 7.57 | 62.67 17.217 12.317 ¢ Warm | 11 | 7.53 | 64.36 17.336 [71032 ea A Cold 9 | 7.57 | 61.62 16.867 11.694 Tal ORAS) |S | Rca 5 | 7.70 | 67.60 17.280 12.050 Alto-| Cold 12 7.57 | 61.91 + 0.79 | 16.954 + 0.110 | 11.850 — 0.076 ‘ gether) Warm 16 7.58 | 65.37 = 0.51 | 17.319 = 0.082 | 12.037 = 0.047 3 Cold 3 8.50 | 66.00 17.617 12.283 Warm | 11 | 8.39 | 67.45 17.677 12.200® Cold 6 | 8.52 | 64.17 17.225 12.183 8—8.9 grams | Q | Warm 8 | 8.60 | 66.62 17.594 12.469 Alto-| Cold 9 8.51 | 64.78 = 1.23 | 17.356 + 0.110 | 12.217 + 0.054 x 4 gether} Warm 19 | $8.48 | 67.11 = 0.45 | 17.642 + 0.052 | 12.313 = 0.054 Cold 8 | 9.32 | 69.25 17.544 12.381 S | Warm 8 | 9.42 | 74.86 17.956 12.587 Cold 15 | 9.46 | 68.33 17.587 12.273 9—9.9 grams | Q | Warm | 10 | 9.57 | 70.90 17.865 12.490 Alto-| Cold 23 9.44 | 68.65 0.57 | 17.572 = 0.069 | 12314 0.035 gether) Warm 18 9.54 | 71.29 =£ 0.30 | 17.906 = 0.041 | 12.533 = 0.034 Cold 20 | 10.48 | 71.70 18.135 12.540 S | Warm | 10 | 10.32 | 68.80 17.975* 12.505* Cold 42 | 10.55 | 71.08 17.675 12.408 10—10.9 grams | 2 | Warm | 17 | 10.34 | 71.35 17.906 12.591 Alto-| Cold 32 | 10.51 | 71.47 = 0.39 | 17.962 + 0.069 | 12.491 = 0.037 gether] Warm 27 10.33 | 70.44% -E 0.47 | 17.931* + 0.050 | 12.559 = 0.043 Cold 12 | 11.50 | 73.42 18.004 12.524 S | warm | 8 | 11.37 | 73.128 18.019 12,669 A Cold 16 | 14.37 || 73.79 17.953 12.544 14—11.9/grams| | 2 | Warm 9 | 11.38 | 73.00% 17.972 12.478# Alto-| Cold 28 | 14.42 | 73.62 + 0.36 | 17.975 = 0.063 | 12,534 = 0.035 gether} Warm 17 | 41.38 | 73.06% + 0.38 | 17.994 = 0.057 | 12.568 =b 0.085 if | cola 9 | 12.52 | 73.33 “| 47.861 12.489 S | Warm | 10 | 12.32 | 72.80° 18.065 12,935 Cold | 7 | 12.37 | 73.43 17.824 12.614 12—12.9 grams | 2 | Warm 8 | 12.49 | 74.75 18.194 12.594% Alto- r Cold 46 | 12.46 | 73.37 + 0.66 | 17.844 0.100 | 12.544 + 0.065 gether] Warm 18 | 12.39 | 73.67 =F 0.42 | 18.122 + 0.052 | 12.783 + 0.053 | Cold 8 | 13.30 | 74.37 18.087 12.656 S | Warm | 09 | 13.33 | 75.67 18.528 12.772 Cold 6 | 13.33 | 74.80 18.350 12.592 13—13.9 grams'| 2 | Warm | 3 | 13.27 | 78.33 18.433 13.050 Alto-| Cold 14 | 13.31 | 74.54 + 0.79 | 18.200 + 0.094 | 12.629 + 0.069 gether] Warm 12 | 13.32 | 7633 + 0.46 | 18.504 + 0.052 | 12.842 = 0.083 Cold 3 | 14.30 | 75.67 18.333 12.617 S | Warm 1 | 14.30 pen 19.000 12.900 Cold 14—14.9 grams | 2 | Worm 1 | 14.10 | 78.00 18.450 12.500 Alto-| Cold 3 | 14.30 | 75.67 18.333 12.617 gether) Warm 2 | 14.20 | 77.00 18.725 12.700 Cold 1 | 15.30 | 80.00 49.300 13.000 S | Warm | 5 | 15.48 | 77.60" 19,0408 13.010 Cold 1 | 15.20 | 78.00 18.350 12.500 Gio ho- 0] Brrs) | SS orate 1 | 15.00 | 76.00 18.800 13.350 Alto-| Cold 2 | 15.25 | 79.00 18.825 12.750 gether) Warm 6 | 15.40 | 77.33® 19.000 13.067 Cold 3 | 16.20 | 7383 19.100 13.050 S | Warm 1 | 16.30 | 82.00 19.450 13.200 Cold 16—16.9/grams | 2 | Warm | 2\ || 16.40 | 83.50 19.100 12.975 Alto-| Cold 3 | 16.20 | 79.33 19.100 13.050 gether) Warm 3 | 16.37 | 83.00 19.217 13.050* Cold 1 | 19.30 | 89.00 19.700 13.200 } Warm Cold 19—19.9 grams 9 Wasi Alto-| Cold 1 | 49.30 | 89.00 19.700 | 13.200 gether} Warm

Archiv fiir Entwicklungsmechanih.

Bad.

XXX.

Table B.

Offspring of Cold-room and Warm-room Parents, measured at 31/, months.

Grouped according to Body Length.

Taf. XVI.

Sumner,

Sex | Parontago|Number| Weight | "0%, | Tail | oot | kar |] Size | sox | Parentage | Numbor| Weight Body | Tail | Foot | Ear g | Lola | 5 3 | Gold 4 | 18.35 | 86.337 | 79.312 | 17.725 | 13.287 8 Warm 1__| 11.60 | 75.600 | 75.400 | 17.350 | 12.850 || 3 Warm 2 | 18.50 | 86.625 | 7.175%) 17.525%) 13.325 Co Te as SHES 2069 LUISE z o g | Sola 2 o | Cold 2 |17.95 | 86.400 | 84.850 | 18.800 | 13.500 Warm i Warm 4 | 18.20 | 86.662 | 84.212" 19.212") 14.050 | go | SR AA ee 12 | Alto-| Cold @ | Alto-| Cold 6 | 18.22 | 86.358 | 80.420 | 18.083 | 13.358 gether| Warm 1 | 11.60 | 75.600 | 75.400 17.350 | 12.850 ___| gether) Warm 6 18.30 86.650 | 81.867 | 17.983*| 13.808 g | cola g | Cold 5 | 19.44 | 87.420 | 79.430 | 17.650 | 13.020 g Warm E Warm 2 | 19.55 | 87.500 | 82.250 | 18.050 | 13.550 a q | Gold 2 | 14.65 | 76.475 | 71.200 | 17.050 | 13.150 || @ g | Lola 4 | 17.45 | 87.525 | 81.125 | 17.700 | 12.962 i | Warm | | | BS _| Warm | 3 | 18.07 | 87.300 | 82.283 | 18.150 | 13.167 © | Alto-| Cold 2 |411.65 | 76.475 | 71.200 | 17.050 | 13.150 ul Alto-| Cold 9 | 18.56 | 87.467 | 80.183 | 17.672 | 12.994 __|gether| Warm | a | gether] Warm 5 | 18.66 | 87.380 | 82.270 18.110 | 13.320 3 Cold | - 3 Cold | 5 20.70 | 88.430 | 80.880 | 17.880 | 13.390 3 Warm | zi eI Warm 4 20.22 88.725 | 81.337 | 18.237 | 13.487 Q ° Cold 1 13.70 | 78.600 | 73.750 _— | 13.150 a ° Cold Kg Warm ce. — eee Ei 7 [ Warm 3 é 18.73 | 88.483 | 84.283 | 18.433 IL 13.667 & Alto-| Cold 1 | 13.70 | 78.600 | 73.750 — 13.150 || 2 | Alto-| Oold 5 | 20.70 | 88.430 | 80.880 | 17.880 | 13.390 gether} Warm EH I gether) Warm 7 19.59 88.621 $2.600 | 18,321 | 13.564 g | Gola g | Gold 6 | 20.18 | 89.400 | $2.270 | 18.200 | 13.400 | Warm ti | g Warm | 11 | 20.89 | 89.495 | §3.686 | 18.055%| 13.700 Q ° Cold 1 15.50 | 79.950 | 79.450 | 17.900 | 13.050 2 2 Cold 1 19.60 | $9.200 | 86.900 | 18.150 | 13.500 2 Warm |_ Sa |e sone | 3 Warm | 2 | 21.65 | 89.575 | 86.200") 18.750 | 14.075 f Alto-| Gold 1 | 15.50 | 79.950 | 79.450 | 17.900 | 13.050 u Alto-| Cold 7 |20.10 | 89.371 | 83.042 | 18.193 | 13.414 ___| gether} Warm | nie f gether] Warm | 43 | 21.01 89.508 $4073 18.162*) 13.758 Cold 3 Cold 10 20.53 | 90.325 | 83.740 | 18.180 | 13.595 4 S | Warm 1 _| 16.20 | 80.550 | 81.250 | 18.000 | 12.850 E Warm | 7 | 20.83 | 90.536 | 84.729 | 18.942 | 13.421* @ Gold 7 | 15.20 | 80.393 | 75.157 | 17.107 | 12.871 || @ q | Lola S| © | warm | 1 | 14.70 | 80.150 | 75,300 | 17.100% 12.730%| © Warm | 1 | 22.30 | 90.000 | 85.450 | 18.600 | 14.450 J Alto-| Gold 7 =| 415.20 | 80.393 | 75.157 | 17.107 | 12.871 L Alto-| Oold 10 | 20.53 | 90.325 | 83.740 | 18.180 | 13.595 gether| Warm 2 | 45.45 | 80.350 | 78.275 | 17.550 | 12.800* gether} Warm 8 | 21.01 | 90.469 | 84.819 | 18.379 | 13.550 se | | i hl Cold 3 Cold 3 21.63 | 91.267 | 84.350 | 18.383 | 13.833 g So | Warm 1 | 16.80 | 81.950 | 75.800 | — 13.600 | & Warm 1 | 20.60 | 91.100 | 85.350 | 18.550 | 13.450* a eS L | = = { oe ee @ Cold 6 | 15.67 | 81.342 | 78.933 | 17.800 | 13.067 || = g | Lola a 2 Warm 2 15.45 | 81.550 | 82.025 18.000 | 13.300 = Warm Be 1 21.80 91.900 | 91.550 | 18.800 | 13.900 t Alto-| Cold 6 | 15.67 | 81.342 | 78.933 | 17.800 | 13.067 i Alto-| old 3 | 24.63 | 91.267 | 84.350 | 18.383 | 13.833 ether) Warm 3 | 15.90 | 81.683 | 79.950 | 18.000 | 13.400 gether| Warm 2 =| 21.20 | 91.500 | 88.450 | 18.675 | 13.675* Bi | ile \¢ | 18 | Cold 2 14.25 | 82.425 | 76.200 | 17.700 | 13.125 3 Cold 6 22.33 | 92.408 | 85.925 | 18.475 | 13.733 i= fs) Warm 1 17.40 | 82.900 | 79.550 | 17.350*| 12.950%) & Warm 3 23.37 | 92.767 | 85.533") 18.383*) 13.950 A a + Q Q Cold 8 15.80 | 82.494 | 75.631 | 17.337 | 13.250 o 2 Cold oS Warm 5 15.82 | 82.610 | 80.490 | 17.770 | 13.090*| & Warm ir | & | Alto-| Cold 10 |15.49 | 82.480 | 75.745 | 17.410 | 13.225 s% | Alto-| Cold 6 | 2233 | 92.408 | 85.925 | 18.475 | 13.733 ether) Warm 6 16.08 | 82.658 | 80.333 | 17.700 | 13.067" ether| Warm 3 23.37 | 92.767 | 85.533") 18.383*| 13.950 B 8 | Cold 3 | 17.40 | 83.717 | 78.250 | 17.800 | 13.150 g | Sala 6 | 22.67 | 93.492 | 87.958 | 18.517 | 13.592 g (c) Warm R Warm | 1 24.30 | 93.250 | 88.350 | 19.100 | 13.800 Q Cold 8 16.79 | 83.419 | 79.200 | 17.550 | 13.212 Ce fe) Cold 3 | 2 | warm | 3 | 16.53 | 83.417 | 80.617 | 18.033 | 13.400 || & Warm IL A Alto-| Cold 11 16.87 | 83.500 | 78.941 | 17.618 | 13.195 L Alto-| Cold 6 | 22.67 | 93.492 | 87.958 | 18.517 | 13.592 gether} Warm 3 | 16.53 | 83.417 | 80.617 | 18.033 | 13.400 gether Warm 1 | 24.30 | 93.250 | 88.350 | 19.100 | 13.800 f Cold 2 16.20 | 84.650 Paral fairl 13.475 Cold 2 23.25 | 94.700 | 89,025 | 18.050 | 13.725 E <} Warm 2 18.35 | 84.725 | 79.300*| 17.650*%| 12.975% 2 3 Warm 4 23.67 | 94.700 | 86.325%) 18.550 | 13.850 a Cold 8 16.79 | 84.519 | 80.887 | 17.843 | 13.469 a fo) Cold ey 2 Warm 3 17.70 | 84.500 | 82.383 | 17.950 | 13.183%) & Warm it : t Alto-| Cold 10 | 16.67 | 84.545 | 80.585 | 17.917 | 13.470 4 Alto-| Cold 2 | 23.25 | 94.700 | 89.025 | 18.050 | 13.725 © | gether) Warm 5 | 17.96 | 84.590 | 81.150 | 17.830% 13.100* gether) Warm 4 | 23.67 | 94.700 | 86.325*| 18.550 | 13.850 Cold 1 18.70 | 85.800 | 81.400 | 17.550 | 12.950 Cold 24.30 | 95.462 | 91.812 g S | Warm 2 |17.60 | 85.425 | 77.325") 17.550") 13.325 || _ Warm = 5 a Cold 6 17.67 | 85.275 | 81.558 | 17.733 | 13.133 & 3 Cold ps 2 Warm 10 18.08 85.570 | 81.180* 18.025 | 13.415 = i Warm 2 : 26.25 | 96.475 | 86.500 | J Alto-| Cold 7 =| 17.81 | 85.350 | 81.536 | 17.707 | 13.107 || & q Cold @ | gether! Warm | 12 | 18.00 | 85.546 | 80.537*| 17.946 13.400, A | Warm 1 | 26.00 | 97.550 | 89.250 a Cold 1 27.20 | 98.900 | 87.000 Warm

Archiv fiir Entwicklungsmechanik. Bd. XXX. Taf. XVII.

Table C.

Offspring of Cold-room and Warm-room Parents, measured at 3!/, months.

Grouped according to Weight.

5 : 7 ; ies) ‘Sex | Parentage |Namber | Weight Baw in| Tail | Foot Bar || oup| Sex |Parentage|Number| Weight] P47 4, | Tail | Foot Ear oa Cold | 2 Cold 12 20.57 | 90.337 | $2.421 | 18.200 | 13.600 2 | S | Warm | 1 | 11.60 | 75.600 | 75.400 | 17.950 | 12,850 | = 3S | Warm | 10 | 20.47 | 80.615 82.520 | 18.195" 13.540* Eb a —| 80 ; = = 5 —— - 11.00 | 76.500 5 I «B50 a Cold 2 ° he 1 76, 69.200 | 16.950 | 13.350 2 ° Cold | | Alto-| Gola 4 | 11.00 | 76.500 | 69.200 | 16.950 | 13.350 f Alto-} Cold 12 | 20.57 | 90.337 | $2.421 | 18.200 | 13.600 — |gether} Warm 1 |11.60 | 75.600 | 75.400 | 17.350 | 12.850* gether] Warm 10 | 20.47 | 89.615 | 82.520 | 18.135*) 13.540* wn Cold a Cold | 8 21.40 | 91.519 | 84.531 | 18.081 13.575 § (s) Warm 7 g 3 Warm {1 |21.55 | 90.159 | 84.600 | 18.200 | 13.605 & fo) Cold 1 12.30 | 76.450 | 73.200 17.150 | 12.950 = 2 Cold a Warm = | Warm | 2 | 21.55 | 90.750 | 90.650 | 18.825 | 13.975 zl Alto- | Gold 1 [12.30 | 76.450 | 73.200 | 17.150 | 12.950 Il Alto-| Cold 8 | 21.40 | 91.519 | 84.531 | 18.081 | 13.575 — | gether) Warm ™ | gether) Warm 13 | 21.55 | 90.250 | 85.531 | 18,296 | 13.662 w Cold 1 13.10 | $2.150 | 79.200 | 18.100 | 13.400 a 6 Cold 5 22.42 | 91.620 | 85.570 | 18.320 | 13.590 a@ | S | Warm 5 Warm | 1 | 22.90 | 94.800 | 83.450%| 18.1008] 14.150 € Semen a : | 2 = ae le Se eh es = ° Cold 1 13.70 | 78.600 | 73.750 | = 13.150 | = ° Cold Go Warm a Warm 2 22.15 | 89.775 84.050 | 18.625 | 14.275 ul Alto-| Gold 2 | 13.40 | 80.375 | 76.475 | 18.100 | 13.275 | | | Aito-| cola 5 pe 91.620 | 85.570 | 18.320 | 13.590 — | gether) Warm ™ | gether! Warm 3 | 22.40 | 91.450 | 83.850*| 18.450 | 14.233 w Cold a Cold 7 23.44 | 93.107 | 87.200 | 18.550 | 13.743 ga | 9 | Warm 2 | 3 | Warm 2 | 23.40 | 93.775 | 87.075*| 18.3754] 13,925 2 2 5 | = 80 eo 5 a 72 +25 th t Cold ee ae a ees | a Alto-| Gold 5 | 14.50 | 80.720 | 74.250 | 17.020 12.880 | a Alto-| Cold 7 | 23.44 | 93.107 | 87.200 | 18.550 | 13.743 “ | gether] Warm 2 |1475 | 81.075 | 77.125 | 17.250 | 13.050 || ™ | gether) Warm 2 |23.40 | 93.775 | 87.075*) 18.375*) 13.925 = cael ie | | and w Cold 2 15.25 | 83.025 | 73.825 | 17.300 | 13.000 wD Cold 3 24.33 | 95.567 | 91.167 | 18.433 | 13.950 E S | Warm Sai i S | Warm | 4 _| 24.45 | 93.787 | 87.912%| 18.900 | 13,900 = o | Cold 40 | 15.47 | 81.755 | 77.735 | 17.585 || 13.060 || = o | Gold 3 Warm 5 15.48 | 82.270 | $1.280 | 17.800 | 13.140 i x Warm Il Alto- | Gold 42 | 15.43 | 81.967 | 77.083 | 17.537 | 13.050 I Alto-| Cold 3 | 24.33 | 95.567 | 91.167 | 18.433 | 13.950 — |gether| Warm 5 | 15.48 | 82.270 | 81.280 | 17.800 | 13.140 | ™ | gether] Warm 4 | 24.45 | 93.787 | 87.912*) 18.900 | 13.900* [sts i ee oAl pack (ieee [ont te SNE: seed | ea Se eee wo Cold 2 16.20 | 84.650 | 79.375 | 18.175 | 13.475 || o Cold 1 25.00 | 95.100 } 94.550 | 18.400 | 13.750 q S | Warm | 2 | 16.50 | 81.250 | 78.525%/ 18.000%| 13.2254) ;| S) Warm ee = ° Cold 18 16.42 | 83.142 | 78.128 17.491 | 13.200 \| &. ° ] Cold cs Warm 5 16.56 | 84.230 | 80.430 | 18.040 | 13.290 is Warm dl lsaess | Gna 20 | 16.40 | 83.292 | 78.252 | 17.563 | 13.227 | Il Alto-| Cold 1 | 25.00 | 95.100 | 94.550 | 18.400 | 13.750 = | gether! Warm 7 | 16.54 | 83.379 | 79.886 | 18.033 | 13.271 | ™ | gether) Warm =I je | ee | eee b oral ieee D Cold 2 17.75 | 85.300 | 74,900 | 17.625 | 13.150 wo Cold § S) Warm 6 17.67 | 85,583 | 77.892 | 17.600*) 13.267 I Gs) Warm 3 | 26.17 | 96.833 | 87.417 | 19.067 | 13.867 = Cold 12 17.36 | 85.075 | 81.025 | 17.783 | 13.283 = Cold 5 2 Warm 10 17.50 | 85.830 | §2.850 | 18.110 | 13.425 é 2 Warm i) Alto- | Cold 14 | 17.41 | 85.107 | 80.150 | 17.761 | 13.264 al Alto- | old — |gether| Warm 16 | 17.56 | 85.737 | 80.991 | 17.919 | 13.366 | ™ | gether! Warm 3 | 26.17 | 96.833 | 87.417 | 19.067 | 13.867 n 3 Cold 5 18.56 | 85.670 | 81.830 17.860 | 13.220 a 3 Cold 1 27.20 | 98.900 | 87.000 | 19.600 | 13.600 q Warm 1 | 18.80 | 84.900 | 81.550*) 17.850%| 12.9508) & Warm Bs ire et fo) Cold 5 18.32 | 86.030 | §4.100 | 18.310 | 13.330 a 2 Cold cs Warm 8 18.52 | 86.237 | 81.800%) 18.194*| 13.450 5 Warm d, Alto-| Cold 10 | 18.44 | 85.850 | 82.839 | 18.085 | 13.275 tl Alto- | Cold 1 | 27.20 | 98.900 | 87.000 | 19.600 | 13.600 — |gether| Warm 9 | 18.56 | 86.089 | 81.772*) 18.156 | 13.394 | ™ | gether} Warm w Cold 11 19.41 | 88.318 | 82.035 | 17.950 | 13.191 I 3 Warm 5 19.52 | 88.440 | 82.460 | 18.012 | 13.440 a Q Cold 1 19.60 | 89.200 | 86.900 | 18.150 | 13.500 & Warm 4 19.62 | 86.725 | 83.362") 18.100*| 13,825 1 Alto-| Oold 12 | 19.42 | 88.392 | 82.477 | 17967 | 13.217 = |gether| Warm 9 |19.57 | 87.678 | 82.861 | 18.056 | 13.611

Sumner,

:: VERLAG VON WILHELM ENGELMANN IN LEIPZIG ::

Uber die Zelle Nachgelassene Schrift

Alfred Schaper

weiland a.o. Professor der Anatomie und Entwicklungs- geschichte an der Universitat zu Breslau

Nach dem Tode des Verfassers herausgegeben

Wilhelm Roux

Mit 3 Textfiguren gr. 8. & —.60

Von dem verdienten, so friih aus dem Leben geschiedenen Forscher lagen bei seinem Tode nur einige Abschnitte der Zellenlehre, die er erst als »Lehr- buch« herauszugeben beabsichtigt hatte, vor. Seinem Wunsche entsprechend, hat der Herausgeber, Herr Geheimrat Prof. Dr. Wilhelm Roux in Halle a. §., fiir die Veréffentlichung dieser, iiber die geschichtliche Entwicklung des Zellbegriffes, die organischen Individualititsstufen und iiber den Bau und die elementarsten Lebenserscheinungen der Zelle, speziell des Protoplasma, handelnden Kapitel

Lehrbuch der mikroskopischen Technik

Professor Dr. Bernhard Rawitz Mit 18 Figuren im Text. Geh. .# 12.—; in Leinen geb. .# 13.20

Physikalische Chemie

der Zelle und der Gewebe

von

Dr. Rudolf Hoéber

Privatdozent der Physiologie an der Universitat Ziirich Zweite, neubearbeitete Auflage Mit 38 Abbildungen im Text 468 Seiten 8. Gebunden 4 14—

: VERLAG VON WILHELM ENGELMANN IN LEIPZIG :

Vortrage und Aufsatze tiber

Entwicklungsmechanik der Organismen

Heft 1:

Heft 2:

Heft 3:

Heft 4: Heft 5:

Heft 6:

Heft 7:

Heft 8:

Heft 9:

Heft 10:

herausgegeben von

Wilhelm Roux

Die Entwicklungsmechanik, ein neuer Zweig der bio- | logischen Wissenschaft. Eine Ergiinzung zu den Lehr- biichern der Entwicklungsgeschichte und Physiologie der Tiere. Nach einem Vortrag, gehalten in der ersten allge- meinen Sitzung der Versammlung deutscher Naturforscher und Arzte zu Breslau am 19. September 1904 von Wilhelm Roux. Mit 2 Tafeln und 1 Textfigur. gr. 8. M d.—

Uber den chemischen Charakter des Befruchtungs- yorganges und seine Bedeutung fiir die Theorie der Lebens- erscheinungen von Jacques Loeb. gr. 8. M —.80

Anwendung elementarer Mathematik auf biologische Probleme. Nach Vorlesungen, gehalten an der Wiener Universitit im Sommersemester 1907 von Hans Przibram.

Mit 6 Figuren im Text. gr. 8. M 2.40

Uber umkehrbare Entwicklungsprozesse und ihre Bedeutung fiir eine Theorie der Vererbung von Kugen Schultz. gr. 8. &M 1.40

Uber die zeitlichen Eigenschaften der Entwicklungs- vorgange von Wolfgang Ostwald. Mit 43 Figuren im Text und auf 11 Tafeln. gr. 8. M 2.80 Uber chemische Beeinflussung der Organismen durch einander. Vortrag, gehalten am 9. Dezember 1908 in der Naturforschenden Gesellschaft zu Halle a. S. von Ernst Kiister. gr. 8. M r1.— ~

Der Restitutionsreiz. Rede zur Eréffnung der Sektion fiir experimentelle Zoologie des 7. internationalen Zoologen- kongresses zu Boston von Hans Driesch. gr. 8. #1.—

Einige Gedanken tiber das Wesen und die Genese der Geschwiilste. Vortrag, gehalten in der Gesellschaft zur Bekampfung der Krebskrankheit, im Januar 1909, St. Petersburg von Priv.-Doz. Gustav Schlater. gr. 8. . 471.20

Das Vererbungsproblem im Lichte der Entwicklungs- mechanik betrachtet von Dr. Emil Godlewski jun. Mit 67 Figuren. gr. 8. MT Uber die gestaltliche Anpassung der Blutgefafe unter Beriicksichtigung der funktionellen Transplantation von A1l- bert Oppel. Mit einer Originalbeigabe von Wilhelm Roux, enthaltend seine Theorie der Gestaltung der Blutgefafe, ein- — schlieBlich des Kollateralkreislaufs. gr. 8. M 4.40

Druck von Breitkopf & Hartel in Leipzig.

Photomount Pamphlet Binder

Gaylord Bros. Makers Syracuse, N. Y. PAT. JAN 21, 1908

Date Due