Februaet 25, 1916] 



SCIENCE 



267 



search; and finally tries to bring his views 

 into accord witli Morgan's discovery- of the 

 artificial astrospheres and Loeb's artificial 

 parthenogenesis. Much space is devoted to 

 the question concerning the relation of centre- 

 some and centriole, a subject which is no 

 longer considered of great importance. In 

 connection with this paper may be mentioned 

 his address before the Versammlung Deutscher 

 ISTatm-forscher und Aerzte 1901, " Das Prob- 

 lem der Befruchtung," where he again puts 

 forward his centrosome theory of fertilization 

 and endeavors to reconcile it with Wilson's 

 new work upon the cytology of artificial 

 parthenogenesis. 



In 1903 Boveri published a preliminary re- 

 port of his work upon multipolar mitosis, 

 which investigation is, in the writer's opin- 

 ion, the acme of his cytological work. Fol and 

 O. Hertwig had discovered the simultaneous 

 division of dispermic sea-urchin eggs into four 

 cells. Driesch had separated these four 

 blastomeres and raised stereoblastulae from 

 them. Boveri now uses this method for at- 

 tempting to analyze the different qualities of 

 the chromosomes in one cell. He demonstrated 

 that the four cells derived from a tetraster- 

 division may get every possible combination 

 of the 3 X 18 available chromosomes ; and that 

 the distribution of normality or deficiency in 

 the plutei raised from the isolated cells corre- 

 sponds exactly to the probable content of the 

 cells in regard to a complete or incomplete set 

 of the qualitatively different chromosomes. 

 These facts are to-day so well known to every 

 biologist that they do not need to be exposed 

 further. But it might be said that the full 

 account of the work published in 1908 as 

 Zellstudien VI., shows Boveri's analytical 

 genius from its very best side; the reading of 

 this work is a highly intellectual and esthetical 

 pleasure. There may be incidentally men- 

 tioned here a short paper on the influence of 

 the sperm on the larval characters of Echinids.* 

 This paper based on hybridization experiments 

 proves, contrary to the views of Driesch, that 

 aU larval characters are influenced by the 

 sperm cell. 



sEoux's Archiv, 16, 1903. 



The same year Boveri reviews before the 

 German Zoological Society the knowledge 

 " Ueber die Constitution der chromatischen 

 Kernsubstanz," a lecture that made a great 

 impression on his hearers through his usual 

 crystalline clearness and keen analysis. It is 

 remarkable because he accepts here unre- 

 servedly the recently published hypothesis of 

 McClung regarding the accessory chromosomes 

 as sex-determiners; further, Suttons's analysis 

 of the relation between the distribution of the 

 chromosomes and Mendelian characters, a 

 hypothesis which Boveri had conceived inde- 

 pendently, but had not previously published, 

 besides a brief remark pointing to his occu- 

 pation with the subject. In this connection it 

 might be said that it is characteristic of 

 Boveri's work that important discoveries are 

 mentioned in his papers occasionally, but not 

 communicated in extenso, because he intended 

 to work them out more fully later. So he al- 

 ways returns to his former observations after 

 a great many years. Meanwhile there may- 

 have been done much work in the same line 

 and ideas proposed from other sides, that he 

 had himself in mind. And this often caused 

 discussions about priority. So Boveri returned 

 in 1905, in Zellstudien V., to his old discovery 

 of 1889 that the size of nuclei in normal and 

 merogonic larvae of Echinids corresponds to 

 the number of chromosomes they contain. 

 The question of size relations between nucleus 

 and cytoplasm had meanwhile become very 

 important through the work of Gerassimoff 

 (1902) and especially E. Hertwig (1903), who 

 tried to base an analysis of many phenomena 

 of cell-life on the assumption of a nuclear- 

 plasmic relation. Boveri now had the ingeni- 

 ous idea of studying the relation between the 

 number of chromosomes and nuclear and cell 

 size by comparing the cells of Echinid larvsB 

 experimentally produced with different chro- 

 mosome numbers. There he had larva, called 

 hemikaryotic, with the haploid number of 

 chromosomes, obtained by artificial partheno- 

 genesis (thelykaryotic) or by merogony 

 (arrhenokaryotic) ; further, the normally fer- 

 tilized, diploid or amphikaryotic larvse, with 

 the normal ntunber of chromosomes, i. e., twice 



