i 34 BIOLOGY AND ZOOLOGY 



E. B. xvii, 520 et seq., and allied articles). He insists on the importance of not being 

 led by misleading analogies. The phylogenetic and systematic value of a character 

 cannot be properly valued until its adaptive character has been understood; the trend 

 of adaptation of the whole organism and of its race should be sought for. The intricate 

 complex of homology and analogy, of adaptation and of change of function, must be 

 analysed, and the little noticed " palaeotelic," non-adaptive characters must be looked 

 for, as they often afford the best evidence of remote relationship. Gregory is restating 

 in somewhat different terms what the present writer urged more than ten years ago 

 (Trans, of the Linnaean Society, 1901, pp. 178 and 270), that a valuation of zoological 

 characters must precede effective application of them to consideration of phylogenetic 

 relationships. Unfortunately it often happens that the systematist, dealing with exist- 

 ing forms, finds notable distinguishing characters which sufficiently unite or separate 

 existing animals, and is therefore content to base 'diagnoses on these. The first distincr 

 tion to be made, however, if phylogeny is the goal, is between characters that are primi- 

 tive and characters which have been modified from the primitive condition. It is plain 

 that the common possession of primitive characters, however convenient a docket for a 

 pigeon-hole, is no guide to affinity. If all the primitive mammals possessed five digits, 

 there is no reason why those that still possess five digits should be more closely allied 

 than any of them may be with those that have lost one or more of the digits. So also 

 modified characters must be analysed; there is no reason to suppose that similar modifi- 

 cations imply affinity, as for instance adaptive modifications or losses of a numerical 

 part of a common heritage. Gregory applies such reasoning in detail to the orders of 

 mammals and has reached many interesting conclusions. 



He thinks that it is unnecessary to have recourse to unknown Amphibian-like crea- 

 tures of the Devonian in the search for the immediate ancestors of the Mammalia. 

 Following Osborn and Broom, he thinks that mammals have been derived from the 

 Triassic reptilian order Cynodontia, although not from any known member of it. He 

 looks specially in these reptiles to the constitution of the temporal arch, the develop- 

 ment of the secondary palate and of paired occipital condyles, the presence of teeth 

 differentiated into incisors, canines, premolars and molars, and to the enlargement and 

 functional importance of the dentary bone and the structure of the limb-girdles and 

 limbs. The Cynodonts " structurally if not genetically " bridge over the gap between 

 mammals and reptiles, for, in combination with the mammalian features that have just 

 been mentioned, they possess many reptilian characters inherited from below. He 

 thinks that the secretion of milk might have been a by-product of the change from cold- 

 blooded reptiles to warm-blooded mammals, and the young reptilian mammals, hatched 

 from eggs carried on the ventral surface of their mother, licked or sucked the secretion 

 because " it tasted good," before it became of economic importance to them. He 

 accepts the evidence that the primitive mammals possessed imbricated scales probably 

 arranged in transverse rows, and that the first hairs were flattened structures protruding 

 between the true scales. 



With regard to the Monotremes, Gregory discusses but dismisses the tempting 

 theory that they were derived from some family of Triassic or Permian reptiles other 

 than that which gave origin to the higher mammals, and holds that the common an- 

 cestors of Monotremes, Marsupials and Placentals were already mammals. The 

 Monotreme stock, however, must have begun to diverge from the Marsupio-Placental 

 remnant at an exceedingly remote period. Not only do the Monotremes retain many 

 primitive reptilian characters not found in higher types, notably in the reproductive 

 system, shoulder girdle and pelvis, but they have also had time to acquire so many 

 deep-seated peculiarities in the skull, that the Monotreme skull may be set in a class by 

 itself, in contrast with the primitive Marsupio-Placental type. There is a balance of 

 evidence in favour of accepting Sceley's view that the Protodonts may be related to the 

 Cynodonts, but in view of the lack of evidence for placing them in either of the mamma- 

 lian sub-classes and of their progressive characters as compared with reptiles, Gregory 

 treats them provisionally as representing a primitive group to which Haeckel's name 



