29 2 R. F. L1C0RISH [april 



(2) " That every change in the needs of animals necessitates other 

 actions on their part for the satisfaction of the new needs, and, in con- 

 sequence, other hahits." 



(3) " That since every new need requires new actions to satisfy it, 

 it demands of the animal which experiences it either the more frequent 

 use of such a part as was formerly less used, so that it becomes con- 

 siderably developed and enlarged ; or the use of new parts which 

 insensibly arise in the organism from the needs, by the efforts of its 

 inner feelings, as I shall presently show from known facts. And to 

 arrive at the true cause of so many different forms, and so many 

 various habits, as are seen in the animal world, one must recognise 

 that the infinitely diversified but slowly changing circumstances in 

 which the animals in each race have successively been placed, have 

 brought about in each race new needs and consequently changes in 

 their habits. As soon as one has recognised this incontestable truth 

 it will be easy to perceive how the new needs can have been satisfied, 

 and the new habits taken on, if one attends to these two laws of 

 nature, which have always been corroborated by observation." 



"First Laiv. — In every animal which has not passed the limits of 

 its development, the more frequent and sustained use of any organ 

 gradually strengthens that organ, develops it, increases its size, and 

 gives it a strength proportional to the use in question ; while the con- 

 stant disuse of such an organ insensibly weakens and deteriorates it, 

 progressively diminishes its faculties, and finally results in its dis- 

 appearance." 



"Second Laiv. — All that nature has caused to be acquired by, or 

 lost to, individuals through the influence of the circumstances to which 

 their race has long been exposed, and therefore through the predomi- 

 nant use of an organ, or through the constant disuse of a part, she 

 preserves by reproduction for the new individuals which come from 

 them ; provided that the acquired changes are common to the two 

 sexes, or to those which have produced the individuals." 



Before entering on the further explanation of Lamarck's key-word, 

 need or desire, I have to point out an almost fatal error in Lamarck's 

 language when stating the above conclusions. Lamarck therein speaks 

 of new needs, but careful consideration of his conclusions has enabled 

 me to see that he really did not mean new needs, but that he referred 

 under such a term to new methods of satisfying the customary needs 

 of animals, as e.g. the need of food, etc. Instead, then, of speaking of 

 new needs he should have said new uses of parts in order to satisfy the 

 functional needs of the animal. This error has been, I believe, a 

 stumbling-block to many in interpreting Lamarck. I myself did not 

 see the error until long after I understood the true meaning of his 

 need or desire. Corrected in the light of this discovery his conclusions 

 read thus : — 



(1) That every change which is at all considerable, and continu- 



