CLASSIFICATION. 133 



. 107. TRANSITIONS. 



The progress of the gradations, in the properties of ho- 

 mogeneous individuals, is termed a transition or passage; 

 and we say of individuals in which such a progress occurs, 

 that they pass into each other. 



These transitions arise from the series of characters before con- 

 sidered ; and individuals connected by transitions are homogeneous, 

 or beloag to one and the same species; there can be no transitions, 

 in such cases, from one species to another, although examples of this 

 sort are sometimes found in minei alogical books. In such instances, 

 it is obvious, if the transition exists, the idea of the species is wrong; 

 for under such circumstances, they should coalesce and form but a 

 single species. 



From the continuity of the transitions, or of the series of charac- 

 ters from which they depend, we may infer that there is a remark- 

 able connexion within the species, by which all the differences oc- 

 curring in its individuals may be joined into a whole. In this way, 

 we are assisted in comprehending the variety of the mineral king- 

 dom. For this reason, it is contrary to the interest of mineralogy, 

 to divide or subdivide the species, and to distinguish subspecies and 

 varieties. The purpose of such divisions is to facilitate the general 

 survey of the species; but this indeed would rather be promoted by 

 establishing the connexion between its individuals, if this should 

 happen to be still wanting, than by subdivisions, which render it 

 less evident. 



In those treatises where this course has been adopted, the student 

 is often greatly inconvenienced, after he has settled the question 

 that an individual belongs to a certain species, to know under which 

 variety it conies ; for it is obvious, that where all the varieties of a 

 species are bound together, as they must be, by intermediary indi- 

 viduals, specimens will occur, which can no more be referred to 

 one variety than to another. Indeed, the effect of such subdivisions 

 is to produce an erroneous idea of the species, as a whole, by caus- 

 ing the pupil to lose sight of those series in the characters of which 

 it allows, and to fix only upon particular members of them, while 

 the remaining ones are wholly overlooked. Accordingly, he is in a 

 condition to recognize those individuals only which are identical 

 with such members of the series as form the varieties in question, 



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