BIOLOGICAL INVESTIGATIONS. 135 



more rapid pace than some suspect." The errors caused by 

 the want of a full realization of this point of view consist 

 largely in sins of omission, as shown by the absence of accurate 

 records. For example, every observation on a species should 

 be dated, location, temperature given, etc., and all the relations, 

 as far as practicable, described, such as habits, food, number of 

 specimens collected, etc. The observations of marine natural- 

 ists, under the leadership of Verrill, have reached a high degree 

 of accuracy in these respects, while those of terrestrial faunas 

 have left much to be desired in some departments, especially 

 Mollusca. 



Observers in all departments, as a rule, have also neglected 

 the obvious manifestations of senility, and treated all animals 

 except man as if they were exempt from growing old. Ap- 

 parently, so far as current descriptions go, the invertebrates 

 and most vertebrates are not affected by senile changes, but 

 simply cut off at the end of their uneventful lives by sudden 

 death, unheralded by any preliminary metamorphoses. Thus 

 conchologists have, for the most part, collected and studied the 

 largest shells with so-called perfect apertures, and described 

 these without any suspicion that they were often dealing solely 

 with extreme senile substages. In fact they have often insisted 

 that these alone were the full-grown representatives of the 

 species, and even in many cases have discouraged the collection 

 and study of the real adults and the younger stages, calling 

 them " immature specimens." 



Such views also enable the observer to see at once the 

 fallacy of classifications and diagrams of the relations of organ- 

 isms that represent them as converging. They diverge from 

 their points of origin, but by no stretching of facts or of the 

 imagination can they be accurately represented anywhere as 

 converging. The series may be parallel, and different genetic 

 series may contain closely representative forms that may have 

 been once considered as belonging to the same genus or even 

 species, 1 but the term "convergence" conveys a false impression. 

 From the genetic point of view no convergence is possible 



1 See Cope, Origin of the Fittest (New York, 1887), and other essays; also 

 Hyatt, " Arietidx," op. cit. 



