Notices of Nefv Books. 7605 



it shows us clearly the highly important fact that an organ originally 

 constructed for one purpose, namely, flotation, may be converted into 

 one for a wholly different use, namely, respiration ; the swim-bladder 

 has also been worked as an accessory to the auditory organs of certain 

 fish, or, for 1 do not know which view is now generally held, a part of the 

 aiiditory apparatus has been worked in as a complement to the swim- 

 bladder. All physiologists admit that the swim-bladder is homologous 

 or ideally similar in position and structure with the lungs of the 

 higher vertebrate animals; hence there seems to be no extreme diffi- 

 culty in believing that natural selection has actually converted a swim- 

 bladder into a lung or organ used exclusively for respiration." This 

 explanation, however necessary, implies, in the early stage of the pro- 

 cess, the multiplication of functions in a particular part, which is 

 diametrically opposed to the theory of advance and complexity of 

 structure being the result of natural selection by the specialization 

 of particular functions to particular organs. It is in the more lowly 

 organized beings that we find a multiplication of functions condensed 

 on a single organ, and a retrogressive process seems to be implied 

 when more functions are applied to an organ than those for which it 

 was designed. 



Another difficulty Mr. Darwin discusses is that presented by the 

 apparent fact of certain organs having been ordained in relation to 

 other organic beings, implying sympathy of design ; ibr instance, the 

 stings of venomous animals as a means of defence. The production of 

 the sting of the bee by natural selection presents a further difficulty, 

 because its exercise involves the death of its possessor, for as its pro- 

 duction can thei-efore confer no dominant advantage upon its owner we 

 should be inclined to view it as a preordained function in relation to 

 the species assailed by it. At page 221 (third edition) Mr. Darwin says : — 

 " Natural selection will never produce in a being anything injurious 

 to itself, for natural selection acts solely by and for the good of each. 

 No organ will be formed, as Paley has remarked, for the purpose of 

 causing pain or for doing an injury to its possessor. If a fair balance be 

 struck between the good and the evil caused by each part, each will 

 be found on the whole advantageous ; alter the lap.se of time, under 

 changing conditions of life, if any part comes to be injurious it will be 

 modified, or if it be not so the being will become extinct, as myriads 

 have become extinct." 



The subject of instinct, treated of in Chapter VII., is discussed as a 

 difficulty, for it is not easy to imagine how those qualities which have 

 such a kindred resemblance to mental power and reflection can have 



