112 Bulletin American Museum of Natural History. [Vol. XXVII, 



of less value as criteria of remote interordinal relationships, than those parts, 

 (such as the brain, reproductive organs, foramina of the skull, auditory 

 ossicles etc.), the relation of which to the environment is more indirect and 

 complex. If, however, any of these sheltered, persistently-surviving palseo- 

 telic organs or characters are brought into more direct relations with new- 

 conditions, either environmental or somatic, they become just as "adaptive," 

 or csenotelic as the rest. For example: (a) the auditory ossicles of the 

 Fissipede Carnivora, as figured by Doran (1879), are in general of a recog- 

 nizable ordinal type, but those of the Pinnipedia, in response to the new 

 acjuatic conditions, rapidly lose this type, and finally, in the most highly 

 specialized forms (the Sea- elephants), take on several superficial points of 

 resemblance to the Cetacean type. (/->) Again, in the brain of the Pinnipedia 

 (Weber 1904, p. 545) the cerebrum retains very strong evidence of relation- 

 .ship with the Fissipedia, but the olfactory parts are reduced — an aquatic 

 adaptation which is accentuated in the Sirenia and Cetacea. 



The })hylogenetic value of palfeotelic characters is occasionally lessened 

 (p. 423) by sudden departures from type, which may be made possible by 

 the lower value of these characters in terms of natural selection. 



Importance of determining the order of appearance of diagnostic characters. 

 — The relative age of different characters should in all cases be a prime ob- 

 ject of research. This historical method (although open to many pitfalls) 

 when judiciously ap})lied seems more likely to lead to lasting phylogenetic 

 results than the time-honored method of setting down all the resemblances 

 and differences between two animals, without further analysis, and then 

 striking; a balance at the end. 



Osteohgij the core of phijlogenetic research. — The last principle requiring 

 notice here is one Avell recognized by many palaeontologists. It is that 

 osteology must after all constitute the core of the true theory of mammalian 

 history. It is only by means of the skeleton that we are able to correlate the 

 knowledge of living with that of fossil mammals and thus to synthesize the 

 results of paUieontology, systematic mammalogy and comparative anatomy. 



Summari/. — Some obvious corollaries of the foregoing principles are: 

 (1) that the phylogenetic and broader systematic value of a character can 

 rarely be appraised with confidence until its general adaptive purpose is 

 understood; (2) that the trend of adaptation of the whole organism and of 

 its race should be sought for; (3) that far reaching homologies and conclu- 

 sions should never be based upon isolated or sporadic resemblances, in 

 possibly cjenotelic characters, between widely removed forms. The phylo- 

 genetic relations of orders recjuires in brief: (1) a consideration of a very wide 

 range of characters drawn from all parts of the organism, (2) a careful 

 analysis of the intricate complex of homology and analogy, of adaptation 



