24 ZOOLOGICAL PHILOSOPHY 



clature would become more difficult to understand than the objects 

 themselves. 



Orders. — The name order should be given to the main divisions of 

 the first rank into which a class is broken up. If these divisions 

 leave scope for the formation of others by further sub-division, these 

 sub-divisions are no longer orders ; and it would be very inappro- 

 priate to give them the name. 



The class of molluscs, for example, are easily divided into two large 

 main groups, one having a head, eyes, etc., and reproducing by 

 copulation, while the other has no head, eyes, etc., and carry out no 

 copulation to reproduce themselves. Cephalic and acephalic molluscs 

 should be regarded as the two orders of that class ; meanwhile, each 

 of these orders can be broken up into several remarkable groups. 

 Now this fact is no sufficient reason for giving the name order or 

 even sub-order to each of the groups concerned. These groups, there- 

 fore, into which orders are divided should be regarded as sections 

 or as large famihes, themselves susceptible of stiU further sub- 

 divisions. 



Let us maintain in our artifical devices the great simplicity and 

 beautiful hierarchy estabhshed by Linnaeus. If we are under the 

 necessity to make many sub-divisions of orders, that is to say, of the 

 principle divisions of a class, by all means let us make as many as 

 may be necessary, but do not let us assign to them any special 

 denomination. 



The orders into which a class is divided should be determined 

 by the presence of important characters extending throughout the 

 objects comprised in each order ; but no special name should be 

 assigned to them that is apphcable to the objects themselves. 



The same thing apphes with regard to the sections that we have 

 to form among the orders of one class. 



Families. — The name family is given to recognised parts of the 

 order of nature in either of the two kingdoms of Uving bodies. These 

 parts of the natural order are, on the one hand, smaller than classes 

 and even than orders, but, on the other hand, they are larger than 

 genera. But however natural famiUes may be and however well 

 constituted their genera are according to their true affinities, the 

 boundaries of these famihes are always artificial. The more indeed 

 that the productions of nature are studied, and new ones observed, 

 the greater the continual variations in the boundaries of families 

 that are made by naturaUsts. Some divide one family into several 

 new ones, others combine several families into one, while others 

 again make additions to a family already known, increase it, and thus 

 thrust back the boundaries which had been assigned to it. 



