Oct. 27, 1887] 



NATURE 



607 



of surface conditions in the distortion of an elastic solid, 

 with the treatment of capillarity, of vortex-motion, and of 

 discontinuous fluid motion {Fliissigkcitsstrahlcti). 



Besides these definite classes of papers, there is a 

 number of noteworthy memoirs of a more miscellaneous 

 character : — on important propositions in the Thermody- 

 namics of solution and vaporization, on crystalline reflec- 

 tion and refraction, on the influence of heat conduction 

 in a special case of propagation of sound, on the optical 

 constants of Aragonite, and on the Thermal Conductivity 

 of Iron. 



Finally we have the series of papers on Radiation, 

 partly mathematical partly experimental, which, in 1859 

 and i860, produced such a profound impression in the 

 world of science, and which culminated in the great work 

 on the solar spectrum whose title is given above. The 

 history of Spectrum Analysis has, from that date, been 

 one of unbroken progress. Light from the most distant 

 of visible bodies has been ascertained to convey a species 

 of telegraphic message which, when we have learned to 

 interpret it, gives us information alike of a chemical and 

 of a purely physical character. We can analyze the 

 atmosphere of a star, comet, or nebula, and tell (approxi- 

 mately at least) the temperature and pressure of the 

 jlowing gas. But, at the present time, the fact that such 

 formation is attainable is matter of common knowledge. 

 f^This is not an occasion on which we can speak of 

 lestions of priority, even though we might be specially 

 attracted to them by finding v. Helmholtz and Sir W. 

 Thomson publicly taking (in full knowledge of a:// the facts) 

 almost absolutely antagonistic views. However these points 

 may ultimately be settled, it is certain that Kirchhoff was 

 (in 1859) entirely unaware of what Stokes and Balfour 

 Stewart had previously done, and that he, with the 

 powerful assistance of Bunsen, MADE what is now called 

 Spectrum Analysis : Kirchhoff, by his elaborate compari- 

 son of the solar spectrum with the spectra of various 

 elements, and by his artificial production of a new line 

 whose relative darkness or brightness he could vary at 

 pleasure ; Bunsen by his success in discovering by the 

 aid of the prism two new metallic elements. 



P. G. Tait. 



ON THE SIGNIFICA TION OF THE POLAR 

 GLOBULES} 



IT has long been known that the egg of some animals, 

 after becoming mature and before undergoing its 

 embryonic development, throws out certain bodies of 

 globular form, which take no part in the embryonic 

 development, but perish sooner or later. These polar 

 globules have been found on the eggs of nearly all classes 

 of animals, and it has been proved that they are real 

 cells, composed of nucleus and cell-body. 



Several theoretical opinions have been expressed in 

 regard to their signification. Some naturalists believe 

 them to be only a kind of excretion of the Gg'g ; others 

 even think them to be of no functional importance, and 

 perceive in them only a remnant of some ancestral process, 

 a recapitulation of some ancient part of the phylogenetic 

 development. 



Now it is true that, in many animals, structures occur 

 without any physiological value, but it is also known that 

 such structures — as, for instance, the hind-legs of whales — 

 disappear more and more in the lapse of phylogenetic de- 

 velopment. Furthermore, such rudimentary organs never 

 disappear in all species and genera of a large group 

 simultaneously, but in one genus or species they persist 

 longer than in another. Thus, some whales possess certain 

 of the bones of their hind-legs lying between the muscles 

 of the trunk, whilst others have preserved only one bone of 



' Paper read by Prof. August Weismann before the British Association at 

 Manchester. 



the pelvis. Now the polar globules might have been 

 regarded as insignificant and rudimentary as long as 

 they were only known in a few groups of the animal 

 kingdom. But as their existence is now proved in nearly 

 all classes of animals, and as they appear in all of them 

 in the same manner, we are compelled to assume that 

 they possess at least some physiological significance. 



Mr. Sedgwick Minot and your illustrious Balfour made 

 a great step forAvard in attempting— each independently 

 of the other — to attribute a high importance to the ex- 

 pulsion of the polar globules. As you know, they suggested 

 that the egg-cell was originally hermaphrodite, and that 

 the polar globules were the male portion, which had 

 to be thrown off. They based their idea upon the 

 generally accepted view, according to which fecundation 

 is the union of a specific male with a specific female sub- 

 stance. If this is true, then the fecundated ovum con- 

 tains both these substances in equal quantities ; and the 

 observations upon the segmentation of the egg lead 

 further to the conclusion of E. Van Beneden, that all 

 cells of the body contain these two substances, and that 

 they are all hermaphrodite. The throwing out of polar 

 globules was, according to these views, the means of 

 preventing parthenogenesis, which must have occurred 

 if the male substance had remained in the egg. This 

 was Balfour's opinion, and he formulated the same with 

 all precaution, putting it forward as a supposition, 

 which might prove true or not. He himself even pointed 

 out the way by which a decision could be obtained, in 

 his statement, that, if his theory was true, polar globules 

 would not be found in parlhenogenetic eggs. Certainly, 

 if polar globules represent the male substance, they can- 

 not be thrown out in an egg that is not destined to be 

 fertilized, and which therefore would not receive the male 

 substance from another cell 



Now, I have tried to decide this question by observing 

 whether parthenogenetic eggs throw out polar globules or 

 not, and I discovered several years ago that polar globules 

 certainly exist in parthenogenetic eggs. I have found them 

 in the summer eggs of Daphnidae, and later, assisted by 

 my pupil Mr. Ishikava, of Tokio, I have also found them 

 in the parthenogenetic eggs of Cypridas and of Rotatoria. 



Now it is impossible that these polar globules can con- 

 tain the male part of the egg, and the question arises, 

 What other significance can be attributed to them ? 



When I ascertained the facts which I have just de- 

 scribed, I was not at the time aware of another fact that 

 I am about to lay before you, and which seems to me to 

 possess an important bearing upon the meaning of polar 

 globules, and of sexual propagation in general. This fact 

 is a very simple one : Parthenogenetic eggs throw out 

 only one polar body, whilst sexual eggs throw out two of 

 them. 



The importance of this fact lies in the significance of 

 the substance that is thrown out in the polar globules or 

 polar cells. You know well that it is a true cell-division 

 which leads to the formation of polar globules, and that the 

 first polar cell takes away from the egg-cell one-half of 

 the nuclear substance. You are also aware that the 

 second polar cell again takes away half of the nuclear 

 substance remaining in the c%z. Hence in sexual eggs 

 three-quarters of the nuclear substance originally con- 

 tained in the egg-cell are taken away by the two polar 

 cells. In parthenogenetic eggs only one polar cell is 

 formed, and consequently only one-half of the original 

 mass of nuclear suostance is reinoved from the egg-cell. 



Now you know that nuclear .ubstance is a very im- 

 portant thing. The experiences and reflexions of the last 

 ten years have led to the general conviction that nuclear 

 substance is the part that controls the whole cell, and 

 that the entire structure as well as the functions of the 

 cell depend upon its minute structure. The nuclear 

 substance is the idioplasma of the botanist Nageli. Upon 

 the molecular structure of it the form and function of every 



