374 Notices of Scientific Works. [July, 



ample. A reference to the author's carefully and conscientiously 

 prepared " Statements as to the duration of the individual in organ- 

 isms " (pp. 55 et seq.), shows upon what slender data he has been 

 compelled to base his conclusions ; for concerning whole groups, 

 hardly anything appears to be known in this respect, and even 

 where our knowledge is less scanty, line after line is preceded by the 

 author's notes of interrogation. 



His conclusions regarding the duration of life in the lower 

 animals are as follows : — 



" Hence, in spite of the great complication of the case, we may 

 conclude, on both deductive and inductive grounds, that the high or 

 low potential longevity of different species, as a general law, is 

 necessitated by those conditions of life which necessitate high or 

 low individual development, as the case may be, whether of bulk, 

 or complexity, or both, that it is directly subject to those conditions 

 which cause personal expenditure to fluctuate, or which affect gene- 

 rative expenditure, being high when these are low, and low when 

 these are high; that these relations, interacting and contending 

 variously according to the special case, determine the potential 

 longevity of the various species of lower animals. 



" From the intricacy of these relations we may conclude that 

 potential longevity is a very delicately balanced quantity, and that 

 very slight causes may produce great fluctuations in it and be 

 almost impossible to trace ; the magnitude of the result being far 

 larger in proportion to the magnitude of the initial cause, as is so 

 often found to happen in biological science " (pp. 87-88). It may 

 be as well to add, by way of explanation, that the author means by 

 personal expenditure, " that involved in the wear and tear of assimi- 

 lating food, and generally carrying on life" (p. 48). 



When he comes to treat of longevity in man, his essay, as might 

 be expected, is more popularly interesting, and its interest is en- 

 hanced by the originality of some of his observations. He attributes 

 a longer life to man in civilization than in a state of nature. 

 " Civilized man/' he says, " lives in societies, one of the most essen- 

 tial bonds of union in which is the maintenance to a greater or less 

 extent by the community of the feeble. The security which the 

 healthy and vigorous man hopes for himself when grown old and 

 feeble he naturally extends to others, and thus the aged are fed and 

 protected as the result of a specific habit or characteristic among 

 men (the most barbarous excepted) " (p. 88). This is the scientific 

 re-statement of the commandment, "Honour thy father and thy 

 mother, that thy days may be long upon the land which the Lord 

 thy God giveth thee." 



The author's account of the rise and spread of our race, and his 

 partial application of Mr. Darwin's theory, only disappoint us by 

 their brevity, and his conclusion is incontrovertible that "individual 



