Dec. 17, 1885] 



NA TURE 



157 



genesis. Balfour suggested " that the function of forming 

 polar cells has been acquired by the ovum for the express 

 purpose of preventing parthenogenesis." Weismann natu- 

 rally cannot agree with this view, since he regards the 

 extrusion of polar bodies merely as the removal of the ovo- 

 genous or spermogenous nucleo-plasma. At the time his 

 memoir was written there were no instances in which it 

 had been ascertained with absolute certainty whether polar 

 vesicles are formed or not in the case of ova about to develop 

 parthenogenetically ; but in a postscript at the end of 

 the memoir he is able to announce that he has discovered 

 that in the case of parthenogenetic summer eggs of the 

 Daphnidce a polar vesicle of distinct cellular structure 

 occurs. This is sufficient proof of the incorrectness of 

 the older theory, and he further adduces the fact that in 

 the case of the honey-bee the same identical egg can be 

 made to develop either after fertilisation or partheno- 

 genetically, according to the act of the queen, showing 

 that the parthenogenetic and sexual eggs are of the same 

 essential nature. The difference between the two must 

 lie in the quantity of germ-plasma which they respectively 

 contain. In order that the segmentation nucleus of the 

 ovum may proceed to the process of ontogenesis, it must 

 possess a certain mass. Even amongst higher vertebrates 

 it is known that an unfertilised egg may occasionally go 

 through the first few stages of segmentation, then, how- 

 ever, always failing through lack of the requisite power. 



When impregnation takes place and the substance of 

 the nucleus of the sperm-cell becomes added to that of 

 the ovum, the combined mass of germ-plasm becomes 

 powerful enough to carry through all the stages of onto- 

 geny to the end. In the case of certain animals where 

 the ovum remains unfertilised, and thus unchanged after 

 the extrusion of the ovogenous nucleo-plasma, if a special 

 supply of nourishment reaches its germ-plasma, this in- 

 creases m amount by growth, and thus attains the mass 

 requisite to start the ontogenetic process, with the result 

 that parthenogenetical development takes place. In the 

 ordinary sexual process it is the sudden doubling of the 

 mass of the nucleus by the copulation that starts the seg- 

 mentation of the ovum. It is the increase of the mass 

 of the nucleus which gives the stimulus to segmentation, 

 the disposition to which was already there before. The 

 difference between eggs requiring fertilisation, and those 

 not requiring it supervenes after the ripening of the egg 

 and the extrusion of the ovogenous plasma. The phyletic 

 inheritance of the capability of parthenogenetic develop- 

 ment rests on a modification of the power of growth of 

 the egg nucleus. 



More than ten years ago Weismann expressed the 

 conviction that "the physiological value of the sperm- 

 cell and egg cell are identical," and now that the 

 body of the egg cell can hardly have ascribed to it a 

 higher value than that of a common nutrient ground for 

 the two nuclei during the act of impregnation, this 

 position seems a very secure one, Strasburger fully 

 agrees, and states that " Sperm-nucleus and egg-nucleus 

 do not differ in their nature." If it were possible to 

 introduce by artificial means into any egg, immediately 

 afterthechangeofthegerminalvesicleinto the egg-nucleus, 

 the egg-nucleus of another egg of the same species, it is 

 probable that the two nuclei would copulate just as if a 

 ripe sperm-nucleus had penetrated into the egg in the 

 usual way, and a direct proof would thus be given that the 

 egg and sperm-nucleus are in fact identical. The tech- 

 nical difficulties are too formidable to permit of this experi- 

 ment being made, but a partial confirmation is afforded 

 by Von Berthold's discovery that in certain algae Ecto- 

 carpus and Scytosiphon, not only a female, but also a 

 male parthenogenesis occurs. Further, the occurrence of 

 conjugation must be regarded as a proof of the correct- 

 ness of this view. There can scarcely be any further 

 doubt that conjugation is the sexual reproduction of uni- 

 cellular organisms. Amongst these usually the two 



conjugating cells are externally absolutely alike, and 

 probably they are so internally also, but there are some 

 low forms, such as Volvox, where a difference between 

 the two is already fully established, huge egg shells and 

 minute zoosperms being produced. The identity of the 

 sperm nucleus and egg nucleus here insisted on only 

 regards their essential fundamental structure and compo- 

 sition ; each is in certain finer details necessarily peculiar, 

 as transmitting the idiosyncracies of its own parent stock. 



H. N. MOSELEY 



THOMAS ANDREWS, F.R.S. 

 T^ R. ANDREWS, whose death we announced a fortnight 

 ■'-^ ago, was a native of Belfast (born December 19, 

 181 3), and spent his whole life there. His father was a 

 linen-merchant, in good position ; and he received his 

 early education at the Academy and at the Royal Aca- 

 demical Institution of Belfast. Thence he went to Glas- 

 gow, where he studied under Dr. Thomas Thomson, the 

 well-known Professor of Chemistry, and learned practical 

 work in his laboratory. He had, next, a successful under- 

 graduate career in Trinity College, Dublin ; where he dis- 

 tinguished himself in Classics as well as in Science. 

 Having spent some time in Paris, in the laboratory of 

 Dumas ; and Having obtained his Medical Degree in the 

 University of Edinburgh, in 1S35 ; he devoted himself to 

 medical practice in his native town. In this he was highly 

 successful ; but he continued to devote his leisure, small 

 as it was, to scientific research ; publishing numerous 

 papers on chemical and physical subjects. To these we 

 will recur, but it is noteworthy that in 1844 he received 

 one of the Royal Medals, in the gift of the Royal Society, 

 for his purely scientific discoveries, before he finally gave 

 up professional practice. He was the first lecturer 

 appointed to teach Chemistry in the Royal Belfast Aca- 

 demical Institution, and he resigned this post, as well as 

 gave up practice, when appointed in 1845 to 'he Vice- 

 Presidentship of the " Northern College," now Queen's 

 College, Belfast. The Presidents and Vice-Presidents of 

 these new Irish institutions were appointed some years 

 before the Colleges were opened, or the Professors elected, 

 in order that the Government might have their advice 

 and assistance in maturing the whole scheme. Andrews 

 was thus associated with another justly-distinguished 

 Irishman, Sir Robert Kane ; and it is mainly to their 

 labours and foresight that the Queen's Colleges, when at 

 last opened, appeared before the world in full working 

 order. 



It had been understood from the first that Andrews 

 was to be the Professor of Chemistry in Belfast ; but, 

 when the time for appointing Professors arrived, he was 

 required (as a matter of form, merely) to produce a few 

 Testimonials. These he obtained at once, in the highest 

 terms, from such men as Thomas Graham, Humphrey 

 Lloyd, MacCullagh, &c., and they need not be given here. 

 But it may be interesting to show, as brietly as possible, 

 the opinions of two of the greatest of foreign chemists. 

 Liebig wrote (November 10, 1845) as follows :—" Ich 

 hege die voile Ueberzeugung dass der Platz um den Sie 

 sich . . . bewerben, keinen wurdigern Besitzer finden 

 diirfte. Sie haben viele Jahre hindurch mit den gross- 

 ten Schwierigkeiten zu kiimpfen gehabt, um der warmen 

 Neio-ung welche Sie fur die Naturwissenschaften hegen 

 Naffrung zu geben, und weit entfernt dass Ihr Muth und 

 Eifer dadurch gelahmt worden ware, haben Sie durch 

 Ihre letzten wichtigen Arbeiten i,iber die Wiirnie bey 

 chemischen Verbindungen dargethan, dass die Beschafti- 

 gung mit der Wissenschaft ein Bediirfniss ihres Geistes 

 ist."'' Dumas (November 29, 1845) wrote :— " Vos titres a la 

 nouvelle fonction \ laquelle vous aspirez sont si clairs et 

 si dvidents que je ne concevrais guereque vous n'y fussiez 

 point appele . . . mais, tout en enseignant la chimie, 

 n'oubliez pas que vous comptez au nombre desphysiciens 



