Haddon — On an Apparatus for Systems of Classifications, ^c. 201 



sequence, and may be varied to any extent. The apparatus which 

 I employ consists of an oblong mahogany board, let into the cor- 

 ners of which are four brass sockets ; into these are inserted four 

 brass standards which are pierced with holes at regular intervals, in 

 such a manner that the holes in each end-standard are vis a vis with 

 those of its fellow, and are at the same time parallel with those at 

 the opposite end. Through these holes brass wires are inserted, and 

 it is upon these that the glass plates rest. This apparatus has the 

 advantage of being readily taken to pieces, and in being quite por- 

 table. 



The names should be printed on paper, then cut out and pasted 

 on two faces of oblong blocks of wood, in such a manner that they 

 can be read in a front view or by looking down vertically upon the 

 apparatus. A makeshift may be constructed by bending a small 

 oblong piece of cardboard roof wise, and writing the name on one 

 face of the anticlinal. 



The several blocks may be linked together in the same plane by 

 pins inserted in the sides, or to those of the plane above by pins 

 placed either vertically or obliquely, and reaching to the upper 

 glass plate. Any complicated system of linkage is thus possible. 



There are two obvious uses to which this apparatus can be put 

 in Zoology, viz., to represent a classification of recent forms and 

 for phylogeny. . 



In a classification of recent forms, each plate might represent a 

 stage of differentiation, and the arrangement of the forms on that 

 superficies would indicate their inter-relationships. The lower 

 planes would naturally be chosen for the less differentiated types. 

 An area on each plane could always be made by a coloured line to 

 represent some special modification. Degraded animals might be 

 tinted, and a black pin slanting from the higher to the degenerate 

 form would graphically show that it was not an ascending type. 

 Missing links between more or less widely-separated living animals 

 could be appropriately supplied by names within brackets. 



For phylogeny the arrangement would be somewhat similar, 

 except that each plate would represent some geological horizon, the 

 name of which would be on a block placed in one corner. Every 

 name in each geological epoch should be tinted in some distinctive 

 colour, so as to distinguish at a glance its precise horizon (it would 

 be well to adopt the Survey colouration). 



