18 POPULAR SCIENCE MONTHLY 



whereas in other cases half an egg will develop only into half an 

 embryo. Investigators are still busy studying out these results, the 

 final interpretation of which has as yet by no means been reached. 

 The experiments have opened to us a new realm of inquiry full of 

 astonishing surprises. 



Experiments on artificial parthenogenesis have been much written 

 about in the daily press, and many absurd things concerning this 

 topic have been printed in the newspapers. Ordinarily the ovum re- 

 quires to be fertilized in order to develop, but it has long been known 

 that certain ova, of bees, of plant lice, of some Crustacea and of other 

 animals will develop without being fertilized. To this process the 

 term parthenogenesis has been applied. Artificial parthenogenesis 

 designates the development of unfertilized ova which normally would 

 not develop at all and which are stimulated to development by placing 

 them under artificial chemical conditions. Doubtless many of you 

 have seen in the newspapers these experiments referred to as if they 

 gave the actual creation of life. Of course that is nonsense. The 

 life is there in the ovum. What artificial parthenogenesis accomplishes 

 is to supply a stimulus, chemical in nature and capable of replacing 

 the fertilization by the spermatozoon, which would otherwise be neces- 

 sary. The possibility of artificial parthenogenesis was first partially 

 demonstrated by Richard Hertwig, but has been perhaps more studied 

 by Professor Loeb, now at the University of California, than by any 

 one else. Hertwig produced artificially only a development of very 

 limited degree, but Loeb by treating the eggs of a sea-urchin for about 

 two hours with a weak solution of magnesium chloride succeeded in 

 1899 in producing larval sea-urchins (so-called plutei) from unfer- 

 tilized ova. He concludes from this that fertilization is a chemical 

 process, and that it is distinct and separate from hereditary trans- 

 mission. No words of mine are needed to emphasize the importance of 

 such investigations, for they are basic. 



A line of work combining experimental and observational methods 

 in which I have been especially interested deals with the problem 

 of growth. It can be shown statistically that the growth of the embryo 

 in early stages goes on at an enormous rate, and also that during the 

 ]ieriod of foetal development that rate is constantly declining, so that 

 something over 98 per cent, of the growth power is lost by the time 

 of birth. After birth decline in the growth power continues, but 

 gradually the decline becomes slower and slower, so that though growth 

 is slight in rate, the growth power is long continued. A study of the 

 condition of cells while this decline of the growth power is going on 

 reveals to us that while the growth power is rapid the nucleus of the 

 cell is active and well developed, and that the protoplasm of the cell 

 is but slightly developed. As the proportion of protoplasm in the 

 cells increases the power of growth diminishes, and as differentiation 



