130 



Mr. W. K. Parker. 



[Jan. 29, 



" new leader " from that stock, and that the Insectivora are more or 

 less transformed modifications of the Marsupial type. I suspect that 

 the existing Insectivora just yield the zoologist one of his groups of 

 types classed together because he knows not what else to do with them; 

 they are not a proper, clear, special branch or " leader " of the Mam- 

 malian life-tree. They form one group under one designation, just as 

 the poor of this metropolis form a group ; their special mark is simply 

 lowliness ; they differ inter se almost as much as the whole remainder 

 above them differ. The higher forms, however, because of their eleva- 

 tion, can afford to be subdivided again into order after order. If we 

 could descend and see the transforming and newly transformed 

 Placentalia of the Eocene epoch, then the morphologist and the zoolo- 

 gist would find common ground ; the taxonomy of the latter, how- 

 ever, would be as useless as the titles and distinctions of modern 

 society to some undeveloped race of savage men. 



The evidently extreme specialization of the existing Monotremes or 

 Prototheria, and their manifest close relationship to the Edentata — a 

 strange lowly group of Eutherians, almost extinct in the old world, and 

 not potent in genera and species in the new — makes it necessary for 

 me in the present stage of my research to leave them until I have 

 mastered both them and the great Marsupial sub-class. Of the latter, 

 however, I can speak already, and as no interpretation of the meaning 

 of the parts seen in a Eutherian skull can be made until they are read 

 in the light of the structure of the quasi-reptilian skull of the Mar- 

 supial, I shall in this paper compare the two types together, using the 

 lower and older, as a measure of the higher and newer, types of skull. 



Anatomists are familiar with the character of the skull in adult 

 Marsupials ; to these may be added others that have turned up to me 

 in the study of their development. When these are seen in the light 

 of the types outside and below the Mammalia, then that which is 

 typical in a high Mammal, as such, can be formulated, and the 

 specialization of this great branch of the Vertebrate stock be under- 

 stood. I will, therefore, here give a list of the more important and 

 striking cranial characters of the Marsupials, promising to bring 

 forward, as early as pos>ible, figures and descriptions of the skull in 

 various stages and in many kinds. But before making this com- 

 parison of the characters of the skull in the Marsupials with what 

 is seen in the Insectivora, I will state that in the latter — a mere 

 order — the diversity is fourfold that to be found in the Marsupials 

 (which are worthy to be put not as a mere order, but as a sub-class), for 

 in them, whether they be eastern or western kinds, the uniformity on 

 the whole is very remarkable, as remarkable as the diversity seen in 

 the Insectivora. The problem put to the morphologist, however, is to 

 explain why the characters that distinguish a Marsupial from a high 

 or Eutherian Mammal are for the most part those which the former 



