February 25, 1916] 



SCIENCE 



269 



own hypothesis — fertilization of one nucleus 

 after a premature division — is the only one in 

 agreement with the facts. 



It has already been said that Boveri's cyto- 

 logieal work was always intermingled with 

 studies in experimental embryology. His 

 favorite objects, sea-urchin egg and Ascaris 

 embryos urged him to work out problems in 

 that line. There may be mentioned only two 

 of his most successful pieces of work. One 

 of these deals with the polarity of the sea- 

 urchin egg. Selenka and Morgan were already 

 acquainted with some of the facts, and the 

 work of Eoux, Driesch and Wilson had 

 brought the discussion of egg-axes, regulation 

 and equipotential systems, to the foreground. 

 Boveri (1901) now is able to demonstrate 

 morphologically the polarity of the sea-urchin 

 egg — the well-known pigment ring— and to 

 point out in a series of experiments how this 

 preformed polarity explains all the previous 

 results r^arding the development of isolated 

 blastomeres, fragmented eggs, deformed germs 

 and larvas with dislocated blastomeres. 



The second series of experiments— partly 

 done in connection with two of his students 

 (Miss Stevens and Miss Hogue) — deals with 

 the potency of the Ascaris blastomeres, studied 

 especially with the centrifuging method and 

 in cases of dispermia. His paper, " Die Poten- 

 zen der Ascarisblastomeren," in E. Hertwig's 

 Festschrift, 1910, constitutes another high- 

 water mark of his work. He mixes the plas- 

 matic content of the eggs by centrifuging 

 them and combines this in other cases with 

 destroying one of the first blastomeres with 

 ultraviolet rays. Then he follows with great 

 accuracy the cell-lineage and reaches through 

 a wonderful analysis the quite unexpected 

 conclusion that in these eggs with strongly 

 determinate cleavage nothing like organbU- 

 dende Keimbezirke can be present, and that 

 these eggs are very probably to be regarded as 

 a " harmonious-equipotential system." In the 

 same paper he gives an answer to another 

 question, which had vexed him, since he first 

 entered the field of cytology, namely, the cause 

 of the diminution of the chromosomes in the 

 somatic cells. By a most remarkable analysis 



he reaches the conclusion that the constitution 

 of the protoplasmic surroundings is alone re- 

 sponsible for the process. 



Besides all this closely correlated work, 

 Boveri only once — with the exception of his 

 doctor's thesis — entered a quite different field 

 of research. The result was his paper on the 

 nephridia of Amphioxus, one of the classics 

 of vertebrate morphology (1892). His dis- 

 covery of the protonephridia of that famous 

 animal, as the result of logical thinking and 

 consequent observation, is well known to every 

 biologist as well as the phylogenetic signif- 

 icance attached to it. In his later years he 

 returned but once to this subject, following 

 Goodrich's discovery of the solenocytes, but 

 always retained a special interest in aU ques- 

 tions concerning the Amphioxus, encouraging 

 also the work in this direction done by his 

 assistant Zarnik. 



The number of papers published by Theodor 

 Boveri is comparatively small, only about 

 forty. But of these there are very few whici 

 could be called unimportant, and a surpris- 

 ingly large number of them constitute land- 

 marks in the progress of our science. This is 

 to be explained by his way of working and 

 thinking. If his ability is to be characterized 

 in a few words, one might say he was keea, 

 philosophic and artistic. Keen, in that hia 

 piercing intellect immediately saw behind a 

 minor observation its far-reaching conse- 

 quences, and followed them patiently to the 

 last detail. Philosophic, as he followed his 

 discoveries and put them in their proper place 

 within the science of biology with an exact 

 logic, sometimes almost striving at dialectics, 

 and with the spirit of clearness and order. 

 And last, but not least, artistic. The con- 

 struction of his ideas has an almost esthetical 

 beauty. And at the same time he was a master 

 of the language. If he talked before a learned 

 society he succeeded, in spite of his calm, al- 

 most monotonous speech, to fascinate every- 

 body, through the clearness and thoughtful- 

 ness of his words, as well as through the 

 wonderfully refined diction. His papers are 

 written in the same spirit; few scientific trea- 

 tises have been better written. And where he 



