34^ 



NATURE 



[November 26, 1914 



PROF. AUGUST U'EISMANX. 



'^T^HERE is a strange and peculiar pathos in the 

 -»- death of this great man, formerly the friend, 

 ue may hope to the last the friend, of so many 

 English naturalists, and in the thought that the 

 gult which had opened between us can never be 

 bridged. For VVeismann was among those who 

 publicly renounced the marks of distinction which 

 had been conferred upon them in this country. 



In the limited space which is available, it is 

 only possible to touch upon the main subjects of 

 W'eismann's scientific career. His earliest re- 

 searches were physiological and histological, the 

 first publication, on hippuric acid (1858), being 

 followed by a series of six papers on the nervous 

 and contractile tissues (1S59-1862). xA.bandoning 

 this subject, except for a single paper on muscle 

 published in 1865, he threw himself with the 

 utmost energy into his classical work upon the 

 embryonic and post-embryonic development and 

 metamorphosis of insects, producing five memoirs 

 between 1862 and 1864, and a sixth in 1866. In 

 the great monograph on the post-embryonic de- 

 velopment of the Muscidae {1864) the building up 

 of the perfect form in the pupa is studied in 

 detail, and it is shown that, in insects with a com- 

 plete metamorphosis, the tissues undergo a break- 

 ing down or histolysis into an apparently simple 

 and primitive mass, from which the imago is built 

 up afresh by, as it were, a second embryonic de- 

 velopment. Thus the long series of slightly modi- 

 fied progressive steps by which, in the more an- 

 cestral groups, the earliest stage is transformed 

 into the latest, has been shortened, in the more 

 recent forms, into a single intermediate stage in 

 which everything is broken down and built up 

 again from the beginning, establishing the truth 

 of Aristotle's statement that " the chrysalis has 

 the potentiality of the egg.'' 



Insect development was followed by a great 

 series of memoirs (1874-1880) on the minute Crus- 

 tacea — Daphnids and Ostracods — and these again 

 by the epoch-makmg researches into the sexual 

 cells of the Hydrozoa, published in four papers 

 between 1880 and 1882, and, in 1883, in the 

 great quarto monograph, "Die Entstehung der 

 Sexualzellen bei den Hydromedusen." With the 

 appearance of this work Weismann's eyesight 

 became too weak for prolonged microscopic re- 

 search, and he turned to other and more general 

 problems of thought and inquiry. 



Weismann was attracted early in his career 

 towards the problems of the history and causes of 

 evolution. "The Origin of Species" appeared in 

 the year following the publication of his first 

 paper, and in 1868 he brought out " Ueber die 

 Berechtigung der Darwin'schen Theorie," fol- 

 lowed in 1873 by his paper on the influence of 

 isolation, written in answer to Wagner. The 

 " Studien zur Descendenz-Theorie " (1875) in- 

 cluded a variety of subjects treated from the 

 evolutionary point of view^ — the seasonal dimor- 

 phism of butterflies, the m.arkings of caterpillars, 

 phyletic parallelism, the transformation of the 

 Mexican axolotl, and the mechanical conception 

 NO. 2352, VOL. 94] 



of nature. This important and stimulating work, 

 translated into English with many additional notes 

 by Raphael Meldola, and with a preface by 

 Charles Darwin, was published in 1882. The 

 present writer well remembers the interest with 

 which he looked forward to the parts as they suc- 

 cessively appeared, and the instant resolution to 

 continue some of the lines of work. 



The central thought which branched forth so 

 luxuriantly during the last thirty years of Weis- 

 mann's life sprang from his researches on the 

 sexual cells of the Hydrozoa. By these he was led 

 to conclude that, however ordinary their appear- 

 ance, the germ-cells cont.ain something essential 

 for the species, something which must be care- 

 fully preserved and passed on from one genera- 

 tion to another. It was this conclusion, so Weis- 

 mann told the present writer in 1887, which led 

 directly to the hypothesis of "The Continuity of 

 the Germ-plasm," with all its far-reaching conse- 

 quences. In Darwin's pangenesis the germ-cells 

 are derived from the body-cells, whereas in Weis- 

 mann's contrasted hypothesis the body is an out- 

 growth from the germ. From this conception 

 Weismann was led to contrast the mortal soma 

 with the potentially immortal germ, and to ques- 

 tion the hereditary transmission of acquired char- 

 acters. Excluded from the Darwinian interpreta- 

 tion of germinal variation as a consequence of 

 gemmules dispatched to the germ by environ- 

 mentally modified body-ceJis, Weismann looked 

 for the origin of variation in the kaleidoscopic 

 combination of innumerable ancestral factors 

 brought about by sexual reproduction. He thus 

 sought to explain the meaning of sexual repro- 

 duction Itself as well as the events which lead 

 up to the fusion of the male and female germ- 

 cells, t 



The subjects thus briefly enumerated, treated in 

 eight memoirs published between 1881 and 1888, 

 were translated and appeared in a collected form 

 in this country as " Essays upon Heredity and 

 Kindred Biological Problems " (1889). The trans- 

 lation of four additional memoirs (1886-1891) was 

 published as a second volume in 1892, the year 

 in which he produced "The Germplasm," 

 translated by Prof. W. Newton Parker, and 

 published in this country in 1893. An elaborate 

 and remarkable hypothesis, "Gernunal Selec- 

 tion" (1896) was followed by the comprehen- 

 sive treatise on the evolution theory, which 

 brought his long and fruitful life-work to a close. 

 The two volumes passed through three editions 

 between 1902 and 191 3, the English translation 

 by Prof, and Mrs. J. Arthur Thomson appearing 

 in 1904, the year of the Festschrift, which cele- 

 brated Weismann's seventieth birthday. 



Weismann was a naturalist keenly interested 

 in living nature, as may be Inferred from "Das 

 Thierleben Im Bodensee " (1877), the fruit of 

 many a holiday spent In the study of aquatic life. 

 He was a delightful and sympathetic companion, 

 possessed of a noble simplicity. To younger men 

 he was generous and sympathetic, and many will 

 remember the encouragement they received from 



