26 REPORT— 1900, 



The first to recognise that morphological relations might exist between 

 the organs of a plant, dissimilar as regards their function, was the poet 

 Goethe, whose observations, guided by his imaginative faculty, led him to 

 declare that the calyx, corolla, and other parts of a flower, the scales of a 

 bulb, (fee, were metamorphosed leaves, a principle generally accepted by 

 botanists, and indeed extended to other parts of a plant, which are referred 

 to certain common morphological forms although they exercise different 

 functions. Goethe also applied the same principle in the study of the 

 skeletons of vertebrate animals, and he formed the opinion that the spinal 

 column and the skull were essentially alike in construction, and consisted 

 of vertebrpe, an idea which was also independently conceived and advocated 

 by Oken. 



The anatomist who in our country most strenuously applied himself to 

 the morphological study of the skeleton was Richard Owen, whose know- 

 ledge of animal structure, based upon his own dissections, was unrivalled 

 in range and variety. He elaborated the conception of an ideal, archetype 

 vertebrate form which had no existence in nature, and to which, subject 

 to modifications in various directions, he considered all vertebrate skeletons 

 might be referred. Owen's observations were conducted to a large extent 

 on the skeletons of adult animals, of the knowledge of which he was a 

 master. As in the course of development modifications in shape and in 

 the relative position of parts not unfrequently occur and their original 

 character and place of origin become obscured, it is difficult, from the study 

 only of adults, to arrive at a correct interpretation of their morphological 

 significance. When the changes which take place in the skull during its 

 development, as worked out by Reichert and Rathke, became known and 

 their value had become appreciated, many of the conclusions arrived at by 

 Owen were challenged and ceased to be accepted. It is, however, due to 

 that eminent anatomist to state from my personal knowledge of the 

 condition of anatomical science in this country fifty years ago, that an 

 enormous impulse was given to the study of comparative morphology 

 by his writings, and by the criticisms to which they were subjected. 



There can be no doubt that generalised arrangements do exist in the 

 early embryo which, up to a certain stage, are common to animals that 

 in their adult condition present diverse characters, and out of which the 

 forms special to different groups are evolved. As an illustration of this 

 principle, I may refer to the stages of development of the great arteries 

 in the bodies of vertebrate animals. Originally, as the observations of 

 Rathke have taught us, the main arteries are represented by pairs of 

 symmetrically arranged vascular arches, some of which enlarge and con- 

 stitute the permanent arteries in the adult, whilst others disappear. The 

 increase in size of some of these arches, and the atrophy of others, are so 

 constant for different groups that they constitute anatomical features 

 as distinctive as the modifications in the skeleton itself. Thus in mam- 

 mals the fourth vascular arch on the left side persists, and forms the arch 



