October 14, 1909] 



NA TURE 



459 



some may be of very ancient date. Wells are so rare 

 in ancient camps on the downs that ponds were prob- 

 ably the chief source of water supply. Why straw 

 was first used, and how it was first used, are likely 

 to remain unanswered satisfactorily. A description is 

 given of a small experimental pond which the author 

 made. The foundations were composed of wood- 

 wool resting on a chalk base, followed by straw and 

 wooden planks, with puddled clay thereon. Further 

 investigations are promised, and no doubt the success 

 O'- otherwise of the pond will form the subject of a 

 future paper. 



In the discussion which followed the reading of the 

 paper. Dr. H. R. Mill claimed that rain is the prin- 

 cipal factor in filling the downland ponds, and sug- 

 gested that the reason why the lowland ponds the 

 more quickly dry up may be that they are not so 

 carefully made watertight as those on the higher 

 Cfround. 



ARTIFICIAL PARTHENOGENESIS.^ 



THE 'development of biology into an experimental 

 science is nowhere better illustrated than in the 

 important researches on artificial parthenogenesis 

 which we owe largely to Jacques Loeb, and biologists 

 will welcome heartily the little book in which this dis- 

 tinguished author gives an account of the subject. 

 Prof. Loeb informs us that the object of his investi- 

 gations was to transfer the problem of the fertilisation 

 (Entwicklungserregung) of the animal e^g from the 

 domain of morphology to that of physical chemistry. 

 He recalls the fact that it is only about sixty years 

 since it was first firmly established that the animal 

 egg — with the exception of a few cases — can only 

 develop into an embryo after fertilisation by the 

 entrance of a spermatozoon. Various interpretations 

 have been placed upon this process. O. Hertwig main- 

 tained that the essential feature of fertilisation was 

 the union of the male and female pronuclei in the egg- 

 cell, and the observation of this union was un- 

 doubtedly of the greatest importance, especially from 

 the point of view of the theory of heredity, but it 

 gave us no real insight into the nature of the stimulus 

 which evokes as its response the segmentation of the 

 ^i^S- Boveri, indeed, maintained that the union of the 

 two pronuclei had nothing to do with providing this 

 stimulus, and was able to show that an enucleated egg 

 may develop after fertilisation ,by a spermatozoon. 

 .\ccording to Boveri the centrosome is the organ of cell- 

 division, and the unfertilised egg cannot develop 

 because the centrosome is wanting. A new centrosome 

 is introduced by the spermatozoon, and then cell- 

 division or segmentation commences. 



Loeb, however, maintains that the development of 

 the egg is a chemical process, depending mainly on 

 oxidation, in which there takes place a synthesis of 

 nuclear material from constituents of the cytoplasm. 

 He accordingly regards the Boverian hypothesis, in 

 which a purely mechanical rdle is assigned to the 

 centrosome, as inadequate to explain the nature of 

 fertilisation. His earliest experiments consisted in 

 treating the eggs of a sea-urchin with sea-water, the 

 alkalinity of which had been increased by the addition 

 of soda-lye. In such water the eggs segmented once 

 or twice, but did not develop further. On the other 

 hand it was found possible to cause the unfertilised 

 eggs to develop into larvje by placing them for a 

 couple of hours in hypertonic sea-water — sea-water, 



^ " Die chemische Entwicklungserregung des tierischen Eie? (Kiinstliche 

 Parthenogenese)." By Jacques Loeb. (Berlin: Julius Springer, 190J. 

 Price q marlts. 



that is, the osmotic pressure of which had been raised 

 about 60 per cent, by the addition of some kind of 

 salt or sugar. This apparently purely osmotic stimu- 

 lation of the egg was subsequently found to comprise 

 two factors, viz., the loss of water by the egg, and 

 the concentration of the hydroxyl-ions of the hyper- 

 tonic solution. It was also found that the hypertonic 

 solution can only stimulate the egg to develop- 

 ment if it contains free oxygen in sufficient 

 quantity. 



The author next succeeded in producing larvae from 

 unfertilised eggs of Chaetopterus by means of potash 

 and acids without raising the osmotic pressure of the 

 sea-water. 



It has long been known that the eggs of many 

 animals, immediately after the entrance of the sperma- 

 tozoon, form a " fertilisation membrane " on the 

 surface. We used to be told that this membrane 

 served to prevent the entrance of additional sperma- 

 tozoa. Loeb attributes to it a much deeper signi- 

 ficance. He finds that in the case of osmotically 

 " fertilised " eggs no membrane-formation takes place, 

 but a short treatment with a monobasic fatty acid 

 causes the formation of a typical " fertilisation-mem- 

 brane " in all the eggs of Strongylocentrotus. If such 

 eggs are then placed for a short time in hypertonic 

 sea-water they all develop into larvae. The artificial 

 membrane-formation by itself, however, in this case 

 only causes the eggs to commence their development 

 without being able to continue it. 



The membrane-formation is regarded as the most 

 important factor in fertilisation. It has also, however, a 

 deleterious effect, a tendency to cytolysis, which requires 

 to be counteracted by treatment with a hypertonic solu- 

 tion, or in some other way. In some species the arti- 

 ficial membrane-formation alone is sufficient to bring 

 about the development of the eggs to normal larvae, 

 the injurious cytolytic effects being less marked than 

 in the sea-urchin. That it is the membrane-formation 

 and not anv other action of the fatty acid which brings 

 about the development of the egg is evident from the 

 fact that membranes produced in any other way have 

 the same effect. 



The author attributes a like importance to mem- 

 brane-formation as the essential factor in the normal 

 fertilisation of the egg by the spermatozoon, and 

 proceeds to inquire what substances and agencies 

 determine such formation. Membrane-formation mav 

 be regarded as a stage in the cytolysis of the egg, and 

 all cytolytic agents will cause membrane-formation. 

 Clearly the cytolvsis must be arrested in some way 

 after the membrane has been formed, otherwise it 

 will lead to the destruction of the egg. Loeb main- 

 tains that in the natural fertilisation of the egg the 

 formation of the fertilisation membrane is brought 

 about by a "lysin," carried by the spermatozoon, 

 which also brings with it a second substance which 

 serves to counteract the evil effects of membrane- 

 formation. 



Such is the essence of the " Lysin Theory " 

 of fertilisation. As an attempt to interpret 

 biological phenomena in terms of chemistry and 

 physics, it is of the greatest interest, though the 

 point of view from which its author regards the 

 phenomena of fertilisation may not be the one which 

 appeals most strongly to students of biology. 



We do not doubt that a new edition of this ex- 

 tremelv interesting work will shortly be called for, 

 and we hope that it may be found possible to publish 

 it simultaneously in German and English. Not the 

 least valuable feature of the book is, to our mind, the 

 introduction of twenty-one pages, in which a concise 

 risitmd of the entire subject is given. 



NO. 2085, VOL. 81] 



