As regards the particular groups of mammals (other than man) in which Flower was more especially interested, there can be no doubt that the Cetacea (whales and dolphins) occupied the first position. And on this subject he was undoubtedly one of the first authorities, his only possible rivals in this country, at anyrate, being Sir William Turner and Professor Struthers. Next to this group came, perhaps, the marsupials, in which a most important discovery was made by Flower in regard to the succession and replacement of the teeth. Not even the most sympathetic of biographers would attempt for one instant to assume that his hero—if a zoologist—could by any possibility be infallible; and it has to be recorded that many changes and amendments have had to be made in Flower’s conclusions. Perhaps, indeed, Sir William has been to some extent especially unfortunate in this respect, owing to the extreme imperfection of the state of our palæontological (I must use the objectionable word) knowledge at the date when much of his best work was accomplished. At that time, in spite of the enormous and valuable results achieved by Cuvier, Owen, and others, mammalian palæontology may be said to have been in its infancy compared to its present state; the wonderful discoveries in North and South America being then either unknown or only partially revealed, and the same being the case with regard to those made known by the working of the phosphorite beds in Central France. These and other discoveries have, for instance, totally revolutionised our ideas with regard to the affinities of the different families of the modern Carnivora, and have thus led to considerable modifications of the views entertained by Flower as to the relationships of the members of this group. Moreover, there is another important factor which has to be taken into consideration. At the time when Sir William wrote his celebrated memoir on the Carnivora, the effects of what is now universally known among zoologists as “parallelism in development” were quite unrecognised. By “parallelism” (to abbreviate the expression) is meant, it may be explained, a remarkable tendency which undoubtedly exists among animals of markedly diverse origin to become more or less like one another in at least one important structural feature, when living under similar physical conditions, or specially adapted for similar modes of existence. Not unfrequently this structural resemblance, when closely examined, is found to be less close than might at first sight have seemed to be the case; the adaptation having been brought about by the modification of structures originally more or less dissimilar towards a common type. In other words, the same goal has been reached by two different routes.