Density of population, in so far as it means what is commonly called over-crowding, is an important factor in the death-rate, and has a most inimical influence upon race-culture--in virtue of the opportunity afforded to the racial poisons--syphilis, alcohol, etc. Thus Sweden has the lowest death-rate in Europe, and has much the least density of population--only 29 per square mile as compared with our own 341. If now the fact of the increase of population, with all that it means and will mean, may be taken as dealt with and accepted, there will be no danger of leading the reader to false conclusions if we insist upon the fall of the birth-rate, which in Great Britain in 1908 was the lowest on record. The death-rate, however, persistently falls also. The reader who thinks that the birth-rate alone determines the increase of population, and those who believe in polygamy on the ground that it necessarily makes for the rapid multiplication and therefore strength of a nation, should compare the death-rate of London, which is under 16, with that of Bombay, which is just under 79. It is asserted that in many large Indian cities the infant mortality approaches one-half of all the children born. What it amounts to in such cities as Canton and Pekin we can only surmise with horror. Notwithstanding the persistent fall in the birth-rate of London the rate of increase in population remains stupendous, according to the calculations of Mr. Cottrell, which may be quoted from the _Science Year Book_ of 1908. He estimates the population of Greater London in 1910 at about 7½ millions, and in 1920 at well over 8½ millions--the falling birth-rate notwithstanding. The increase of population of five great countries may be briefly noted here. In all, with the possible exception of Russia, the birth-rate is rapidly falling. In the course of the nineteenth century the population of Russia (in Europe) rose from 38 to 105,000,000 France " " 26 " 38,000,000 Germany " " 23 " 55,000,000 Great Britain " " 15 " 40,000,000 United States " " 5 " 75,000,000 These are merely approximate figures, but accurate enough to be of value. It need hardly be pointed out that immigration accounts for the disproportionate increase of population in the United States. But it may be added that the imminent arrest or control of this immigration will assuredly have the most serious and pressing consequences for Europe. Plainly it must hasten the coming of national eugenics.