170 CONVERGENCE IN MINUTE STRUCTURE 



of orthogenesis and convergence. A greater 

 assemblage of facts than has been marshalled 

 here would be necessary, nothing short of a 

 new cyclopaedia of anatomy and physiology, and 

 probably the time is not yet ripe for that. Up 

 to the present no other work with which I 

 am acquainted has dealt with convergence as a 

 general and positive phenomenon of equal import- 

 ance with orthogenesis or normal morphology, 

 although isolated cases are referred to in most 

 text-books of zoology and are exhibited in most 

 natural history museums. 



The fact that no laws of convergence are or 

 even can be laid down now is one which is 

 fraught with the greatest hope for the future 

 of morphology ; and the breaking down of the 

 former landmarks of homology, such as histo- 

 logical structure and metameric repetition, except 

 within narrow limits, offers a great opportunity 

 for emancipation from the trammels of specu- 

 lation. If we were to tabulate laws they would 

 not be natural, but merely dogmatic, at the mercy 

 of the first unbeliever. Hardly one universal 

 criterion of strict homology can be mentioned 

 which would pass muster in a critical examina- 

 tion. Then away with laws and away with 

 criteria until they cease to obscure the facts as 

 they are. 



Hypotheses are one of the chief means of 

 progress in morphology. Without them the 



