LINNEAN SOCIETY OE LOKDOTf. 27 



species, but ouly individuals wliicli succeed each other, and re- 

 semble those which produced them. But these individuals belong 

 to infinitely diversified races which present shades of distinction in 

 all their forms and in all their degrees of organizatiou, and each 

 one of which maintains its character without mutation so long as 

 no cause of change acts upon it^ 



He wrote : — " There is an order in Nature, and it can be recog- 

 nized by the structural affinities of liviug bodies. It is the least 

 recognizable when forms are at the extremities of a scale, and 

 when their organization presents the greatest possible differences. 

 This order, recognized by relations of structures, should replace 

 all artificial systematic classifications." 



Lamarck proceeds to define the primary classificatory terms, 

 and recognizes the beauty and value of the orders of Linufeus. 



In considering the structural relationships of animals, Lamarck 

 places the organs in the following order in reference to their 

 importance — those of locomotion, respiration, circulation. "With 

 regard to the Vegetable Kingdom, he considered the order to be 

 — the embryo and its accessories, the sexual parts of the flower, 

 the floral envelopes, the envelopes of the seed, and the re- 

 productive bodies, " qui u'ont j)oint exige de fecondation." It 

 was after studying their structural relations that Lamarck 

 stated he recognized that the Infusoria could not be associated 

 with the Polypes in the same class, and that the Eadiata could 

 not be confounded with these last — that the Vermes were an 

 isolated section, that the Arachnida could not be classified with 

 the Insecta. He was able to point out, on this plan, that the 

 break was vast between the highest Invertebrate, which he con- 

 sidered might be one of the Heteropoda, aud the possessor of 

 the simplest osseous or cartilaginous spinal column. 



Lamarck then considers the genus ; but time will ouly permit 

 me to select passages from his works relating to species. He 

 suggests that the endeavour to define what is called a species 

 and the attempt to discover whether species are absolutely con- 

 stant and as ancient as Nature herself — haviug lasted on, as they 

 now are — are not necessarily futile undertakings. On the other 

 hand, he says it is worthy of consideration whether species have 

 or have not been subjected to changes of circumstances which 

 have been relational to them, although acting with exceeding 

 slowness, aud whether specific forms have or have not changed 

 in character and shape during lapse of time. 



He states that the elucidation of this question of modification 

 is not only of interest to our zoological and botanical knowledge, 

 but is necessary for our comprehension of the history of the 

 earth. 



Then comes the celebrated definition of species : — "A collection 

 of similar individuals which were produced by other and similar 

 individuals." Lamarck proceeds: " This definition is exact ; for 

 every living creature nearly re>embles those which produce it." 

 " That the species," he writes, " is constant is not true ; it is not 



