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XII. Observations on Genera. By H. T. Stainton, Esq. 



[Read December 1st, 1856.] 



There are probably many persons who have hardly given any 

 serious consideration to the nature of genera. A knowledge of 

 species is no doubt the first and most important step the naturalist 

 has to make, but yet as genera do exist, it is desirable that some 

 clear conception should be attained, if practicable, of what con- 

 stitutes a genus. 



A genus is a collection of species which agree more or less 

 rigorously in the possession of certain definite characters. 



Combined with this agreement in structural character, we shall 

 generally find a considerable degree of uniformity of habit. 



A perfect uniformity in the structural character is not to be 

 anticipated in any genus, and where by accident we do meet with 

 it, it can only arise from such genera being extremely limited in 

 extent, and the somewhat abnormal species belonging to them not 

 having yet been discovered. 



Just as we find from that infinite variety in nature that hardly 

 two leaves of a tree are exactly similar in every respect, hardly 

 two specimens of a species are precisely alike, so we should not 

 be surprised to find, were the different species of a genus minutely 

 examined, that there is more or less structural diversity amongst 

 them. 



The question, what amount of diversity of structure should 

 necessitate the removal of a species from a genus, is of course 

 always open to much discussion. 



Manifestly it would not be desirable to have as many genera 

 as species ; if we had, we should entirely lose the object which 

 we gain by the acceptance of genera. Say, for instance, we have a 

 genus composed of twenty species : we are aware, if we know the 

 name of any one species, that it is related more or less intimately 

 to the remaining nineteen. But supposing the whole twenty are 

 divided into as many genera: then, when we learn the name of a 

 species, we learn nothing of its relations ; we are obliged to put a 

 second question — " What genus does it come next to?" 



Now, if the genus cannot consist of species all mathematically 

 agreeing in structure, and if it is found unadvisable to create new 



VOL. IV. N. S. PT. v. — JULY, 1857. I 



