1 36 Mr. W. S. MacLeay on the Dying Struggle 



from pure Grecian to the pure Gothic architecture. The 

 continuity, wheresoever as to space the kirks intermediate in 

 structure may be placed, will be perfect so far as relates to the 

 gradation of form. And yet there must ever be some differ- 

 ence between the two structures nearest each other in form ; 

 for if no interval exists, then these two must have the same 

 structure, and one of them will thus produce no effect in con- 

 tinuing the chain of structure. In this kind of continuity, 

 therefore, intervals between different forms are absolutely ne- 

 cessary ; and if they do not exist, there is only one form. In 

 space or time, which afford the only continuity that Dr. 

 Fleming can comprehend, an interval is impossible; and 

 their continuity depends on this impossibility. On the other 

 hand, continuity in gradation of structure depends on the 

 existence of intervals ; but requires, in order that the gradation 

 be more distinct, that these intervals be extremely small and 

 numerous. If only one mean be interposed between two ex- 

 tremes, there will be two chasms but no salhis, and the three 

 objects will be in continuity. Augment the number of various 

 intermediate objects, and you only get the chasms more nu- 

 merous and the continuity more perfect. To chatter there- 

 fore about the innate impossibility of the law, is absurd : the 

 only question for us now to examine, being, whether such a 

 continuity as I have described can be shown to exist in 

 Nature. 



I think I have proved this in my Analysis and Synthesis of 

 Petalocerous Coleoptera. You, my dear Vigors, have proved 

 it in Birds; and what the Linnaeans call natural genera, such 

 as Rosa and Erica, are likewise all proofs of it: so that if con- 

 tinuity manifestly holds good in these particular parts of the 

 Creation, which have been carefully examined, it may hold 

 good in all. True it is that Nature does not always proceed 

 pari passu. In the Linnaean genus Psittacus, a group of very 

 limited structure, the chain is composed of an immense num- 

 ber of links; whereas, in Pachydermata, a group presenting a 

 very wide range of structure, the number of links is compara- 

 tively small. Still there is continuity manifest in both ; the 

 difference depending merely on the relative distance between 

 some two contiguous forms in each. Chasms in the chain may 

 be numerous and small, as in Psittacus, or few and wide, as 

 in Pachydermata • but an hiatus is not synonymous with a 

 saltus. 



Some years ago, in a paper in the fourteenth volume of the 

 Linnaean Transactions, I stated it as an undoubted fact, that 

 hiatus or chasms are every where in nature presenting them- 

 selves to the view; and I think I have now satisfactorily ex- 

 plained 



