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SCIENCE 



[N. S. Vol. XLIII. No. 1104 



as many as the foregoing, then diplokaryotic 

 larvse, again with twice as many chromosomes 

 as the last, produced by artificial suppression 

 of the first cleavage figure. Now by com- 

 paring these larva he found that the surface 

 of the nuclei is proportional to the number 

 of chromosomes contained in them; that the 

 size of the cell is again proportional to both; 

 and that the number of the cells in the same 

 stage is inversely proportional. It does not 

 need to be said that he discussed all conse- 

 quences from these facts, in their different 

 aspects. It is well known that these discus- 

 sions are still going on, especially in connec- 

 tion with the work of R. Hertwig and his 

 pupils and of Conklin. 



The ever-growing tree of cytological re- 

 search had meanwhile developed another 

 flourishing branch. Henking had discovered 

 (1891) the facts about the accessory chromo- 

 somes without understanding their importance. 

 The studies of Montgomery and Sutton again 

 revived in the beginning of the century the 

 interest in these facts. McClung recognized 

 in 1902 their importance for the sex-problem, 

 and the work of Miss Stevens and especially 

 Wilson brought the most surprising clearness. 

 Boveri immediately became interested in these 

 questions and suggested to some of his stu- 

 dents lines of work in that direction. In 

 1909 he reported before the " Physikalisch- 

 medizinische Gesellschaf t " in Wuerzburg, 

 where practically all his discoveries were first 

 communicated. Miss Boring's work, discover- 

 ing the very important Ascaris type of sex- 

 chromosomes ; further about von Baehr's work, 

 who cleared up simultaneously with Morgan 

 the interesting behavior of the sex-chromo- 

 somes in the male cells of aphids; further 

 about Gulick's studies on the sex-chromosome 

 cycle of Strongylids, especially important be- 

 cause he was the fh'st to work out in detail 

 the conception that sex-linked characters are 

 carried by the x-chromosome ; finally Baltzer's 

 work about sex-chromosomes in female Echi- 

 nids (which later had to be revoked after 

 Tennant's work). Boveri himself studied the 

 sex-chromosomes in hermaphroditism (1911) 

 and succeeded, simultaneously with Schleip, 



in bringing the facts in harmony with the 

 general, conceptions; the object was the 

 nematode Rhabditis nigrovenosa, which shows 

 an alternation between hermaphroditic and 

 bi-sexual generations. 



The last years of Boveri's life gave to us 

 three more papers in the general field of cytol- 

 ogy, each one showing him still at the summit 

 of his intellectual strength. The first, " Ueber 

 die Charaktere von Echinidenbastardlarven bei 

 verschiedenem. Mengenverhaeltnis muetter- 

 licher und vaeterlicher Substauzen " (1914), 

 gives a very fine analysis of the relative im- 

 portance of protoplasm and nucleus in the in- 

 heritance of characters. By comparing hybrid 

 larvffi with different qualities of both (devel- 

 oped from giant-eggs, fragmented eggs, iso- 

 lated blastomeres) he reaches the conclusion 

 that the chromosomes are responsible for the 

 characters of the larvse (in agreement with 

 Baltzer and Herbst and opposed to Godlevski). 

 In the second paper, " Zur Frage der Entste- 

 hung maligner Tumoren " (1914) we find 

 Boveri in a field at first sight far distant from 

 his usual line of work. But only apparently. 

 In his former analysis of the chromosomes 

 in multipolar spindles he had already pointed 

 to the possibility of explaining the sudden 

 origin of malignant tumors and their behavior 

 by the assumption that they originate from 

 cells with abnormal combinations of chromo- 

 somes resulting from an occasional multipolar 

 mitosis produced by some influence in the 

 siirrounding medium. As he believes that this 

 idea, very closely connected to von Hanse- 

 mann's cancer-theory, might be useful for 

 further research, he works it out here in ex- 

 tenso and discusses its merits in regard to the 

 facts of pathology. The third paper finally, 

 and the last one published by Boveri during 

 the summer 1915, deals again with a subject, 

 discussed by him 27 years before, namely, the 

 origin of Siebold's famous gynandromorphic 

 bees from the Eugster hive. Boveri was able 

 to secure the original material and to work it 

 through in order to determine whether his old 

 hypotheis of 1888 or those of Morgan (1905) 

 or Wheeler (1910) was correct. By means of 

 a very beautiful analysis he shows that his 



