72 THIRD GENERAL MEETING. 



while the methods of investigation were not adapted to insure a 

 satisfactory answer. The present discussion is on a much higher 

 plane, and the previous speakers have made an admirable presen- 

 tation of their side of the case. I cannot, however, quite agree with 

 them as to the value of the facts and theories they have presented, 

 and shall consider the question from another point of view. 



The Mammals, as we know them to-day, are classed by them- 

 selves, yet contain such diverse groups that it may fairly be regarded 

 an open question whether all have a common origin. The attempt 

 to ascertain whence they came is likely to bring out indications that 

 they may have had several sources of origin, and this, if so, may 

 help to explain the great diversity among them. 



It is of course evident that some of the most characteristic 

 features of recent mammals, for example, the hairy covering, the 

 circulatory system, and the milk glands, cannot be used in a 

 comparison with fossil forms. The osseous structure only is now 

 available in the early mammals and other vertebrates, and in this 

 alone points of resemblance must be found if different groups are 

 connected genetically. 



In considering the relations of reptiles to mammals so far as the 

 fossil forms are concerned, which seems to be the main question 

 before us to-day, I have only time to speak of the skull, and shall 

 refer to some of its salient features already mentioned in this 

 discussion ; namely, the teeth, the squamosal bone, the quadrate, 

 the occipital condyles, and with them the lower jaw. These perhaps 

 may serve as crucial points in distinguishing the skull of a reptile 

 from that of a mammal, even if they fail to indicate a near affinity 

 between them. 



The different kinds of teeth seen in the reptiles regarded as 

 mammalian in type, I consider of comparatively small importance, 

 for the reason that the same general forms of teeth are to be found, 

 not merely in the reptiles supposed to be nearest to mammals, 

 but also in other groups widely different. In the Crocodiles, for 

 example, the extinct genus NotosiLcJms, recently discovered in 

 Patagonia, has all three kinds of teeth well distinguished. Again, 

 some of the Dinosaurs, especially the genus Triceratops, have teeth 

 with two roots, a supposed mammalian character. In some Fishes, 

 also {AiiarrhicJias), three kinds of teeth may be seen. It is more 

 than probable, therefore, that the peculiar resemblance between the 

 teeth of mammals and those of the lower vertebrates is merely one 

 of parallel development, the adaptation being along similar lines, 

 and in no sense an indication of genetic affinity. 



The great development of the squamosal bone in Theriodonts 

 is not seen in them alone, for somewhat similar proportions are found 

 in some other reptiles, for example, in the Plesiosaurs, where the 

 squamosal is very large, and wrapped round the quadrate. In some 

 of the Dinosaurs, also {Torosatwus), the squamosal has an enormous 

 development, while the quadrate remains of very moderate size. 



