August 6, 1886.] 



SCIEJSfCE. 



m 



■nations of Flemming ^"^ and of several other recent 

 authors seem to me conclusive." The footnote 

 communicates more fully the further significant 

 fact, that the male element is developed chiefly 

 from the chromatine of the nucleus. The facts 

 stated prove that a body consisting mainly of 

 chromatine from the nucleus of a sperm cell can 

 impregnate an ovum. 



Oskar Hertwig was the first '* to point out the 

 bearing of this induction upon the problem of 

 heredity. It is obvious, since qualities may 

 be inherited from the fathei", that the nucleus 

 alone can furnish the means of transmission from 

 parent to oti'spring. And, since it can accomplish 

 this on the paternal side, it is probable that it can 

 do as much on the mother's side, an assumption 

 against which no evidence has been brought for- 

 ward : hence the hypothesis that the nucleus is 

 the organ of hereditary transmission. Further, 

 since the chromatine is the characteristic of the 

 nucleus, and since spermatozoa in some cases con- 

 sist almost exclusively of chromatine, it is proba- 

 ble that chromatine is the essential factor in the 

 function of heredity. The leading defenders of 

 this double hypothesis are Hertwig, Strassburger, 

 and Koiliker, all biologists as able as they are 

 distinguished. Careful study of their writings 

 must, I think, lead a candid mind to accept their 

 argumentation ; though of course one does not 

 forget that hypotheses are not demonstrations. 



Hertwig's paper ^* is to be recommended as the 

 best single essay, the one to be read by those who 

 desire to grasp the essential points of the discus- 

 sion of heredity, and yet have not the leisure to 

 go through all that has been published. Hertwig 

 writes admirably : his matter is well arranged, his 

 language direct, and his thinking clear and forci- 

 ble. In brief, his papers have many of the quali- 

 ties which we expect in a model of scientific 



12 Archiv filr mikrosk. anat., xviii. p. 310. 



13 The following authorities covering the period of the 

 last eighteen months have dealt with the development of 

 the spermatozoon in mammalia : Brown, Quart, journ. 

 micros, sc, xxv. 313 ; Wibdbrspbrg, Arch. f. mikrosk. 

 anai.. XXV. 113 ; Platneh, Ibid., xxv. 564 ; Biondi, Ibid., 

 xxv. 594 ; Plainer, Ibid., xxvi. 348 ; La vallette St, 

 George, Ibid., xxvi. and xxv. 581. Others might be cited. 

 I have given a synopsis of these researches in the Boston 

 medical and surgical journal, cxiv. 460. Nussbaiim, even 

 in his latest paper, adheres to his belief that the sperma- 

 tozoa are always cellular, and not exclusively nuclear. 

 Unfortunately he does not state upon what grounds the 

 results of so many investigators are to be set aside. The 

 authors cited show that the chromatine gathers together 

 within the nucleus, and that it forms the head of the sper- 

 matozoon, while a large part of the nucleus breaks down : 

 hence the spermatozoon arises chifly from the chromatine 

 of the nucleus of the cell (spermatoblast). 



1^ ' Das problem der befruchtung und der isotropic des 

 eies, elne theorie der vererbung,' in Jena zeitschr. natur- 

 wissensch., xviii. 



writing. Some of his later ones exhibit less care- 

 ful preparation. 



Johannes Frenzel '^ has published what may be 

 characterized as a lengthy, and on the whole half- 

 hearted, criticism of the hypothesis of Hertwig. 

 The objections he brings forward are in large 

 part those which necessarily occur of themselves 

 to every competent judge of the problem. An 

 older investigator would have perceived this, and 

 accordingly dealt with the discussion with much 

 greater brevity. Frenzel's first objection is, that 

 it is not certain that the nuclei of the male ele- 

 ments are not still accompanied by some proto- 

 plasm when they fuse with the ovum. Unfortu- 

 nately our author has overlooked that the best 

 investigations show the mammalian spermatozoon 

 to be derived solely from the nucleus. Frenzel's 

 second objection is that there are cells without 

 nuclei. Careless and incomplete observations have 

 frequently led to the assertion that there are such 

 cells, but the error has been again and again re- 

 futed. On pp. 1)7-98 Frenzel cites Bobretzky and 

 Korotneff as authorities, but these authors have 

 not made sure of the absence of the nuclei. On 

 the contrary, their investigations on the insect 

 eggs, in which cells without nuclei are supposed 

 to occur, are so obviously insufficient that it is 

 astonishing to find stress laid upon them. For 

 my own part, I feel little hesitation in asserting 

 that except, perhaps, among the very lowest or- 

 ganisms, there are no cells loithout nuclei. As 

 regards the lowest organisms, there is uncer- 

 tainty. Nothing to be called a nucleus is known 

 in bacteria, for instance. We cannot, indeed, 

 state at present that the continuance of life is im- 

 possible without a nucleus. On the other hand, our 

 knowledge of the minute fungi and supposed mone- 

 ra is so imperfect, that it would be foolish to accept 

 the dogma that these organisms have no nuclei. 

 It is conceivable that in the lowest forms of life 

 the material basis of heredity is a diffused sub- 

 stance, which in the progress of evolution has 

 gathered together to result in the genesis of nuclei. 

 Thei'efore, whether the lowest bionts are nucleate 

 or not, they do not offer, so far as at present 

 known, any valid objection to Hertwig's theory 

 that the nucleus is the organ of heredity. There 

 is nothing else in Frenzel's article requiring notice 

 in this brief review. It will not, I think, repay 

 those not engaged in the special study of the sub- 

 ject to familiarize themselves with the essay in 

 question, for I am able to commend it only with 

 reserve. 



The last few years have not only brought us 



^'■> ' Das idioplasma und die kernsubstanz,' in Archiv fiir 



mikros. anat., xxvii. 18H6, pp. 73-lv!8. Frenzel's position is 



best shown by a paragraph on p. 89 which summarizes his 



