422 JAMES PERRIN SMITH 



Is it to be wondered at, then, that the student of mor- 

 phology becomes a sceptic, or even a rank unbeliever with 

 regard to the value of ontogenic stages as records of history? 

 It is only to be expected that the biologist, especially one that 

 deals almost exclusively with living species, should be inclined 

 to discredit the law of tachygenesis, and to believe that there is 

 such an inextricable muddle of omissions, secondarily introduced 

 characters, and unequal acceleration of those actually repeated, 

 that the record is wholly untrustworthy, or at least illegible. 

 And yet there are so many species and genera in the various 

 groups of invertebrates whose ontogeny is simple, progressive 

 and fairly complete, and whose stages of growth are almost 

 exact repetitions of successive antecedent genera, that it would 

 be impossible to find a student of the morphogeny of the 

 brachiopods, the marine mollusks, or the lower crustaceans, that 

 does not believe implicitly in the value of larval stages of these 

 groups as records of their family history. And this is especially 

 true of the paleobiologists, who regard it of little importance 

 whether the animal under investigation died yesterday, during 

 the flood, or during the Paleozoic era, whether it is preserved 

 in alcohol or in a more permanent museum in the bosom of 

 mother earth ; they recognize the fact that the life-history of a 

 Cambrian trilobite has as much bearing on modern biology as 

 does the history of the living crayfish, and that the laws that 

 govern the rise and decline of organisms were just as true then 

 as now. 



Not all groups are equally useful to the student of morphog- 

 eny, but in each of the lower subkingdoms there are genera of 

 which the ontogeny has been studied and correlated in no uncer- 

 tain terms with the history of the race. The testimony of these, 

 various groups is so uniform, notwithstanding the fact of its hav- 

 ing been gathered by men of different beliefs, that its value can- 

 not be doubted. It is also noteworthy that in the higher groups, 

 such as cephalopods and crustaceans, the evidence and the cor- 

 relations are much more decided. 



