6 REPORT— 1881. 



Miocene, tliree ; and that it is not till the Uppei- Pliocene that we find 

 any species with the magnificent antlers of our modern deer. It seems 

 to be now generally admitted that birds have come down to ns through 

 the Dinosaurians, and, as Huxley as shown, the profound break once 

 supposed to exist between birds and reptiles has been bridged over by 

 the discovery of reptilian birds and bird-like reptiles ; so that, in fact, 

 birds are modified reptiles. Again, the remarkable genus Peripatus, 

 so well studied by Moseley, tends to connect the annulose and articulate 

 types. 



Again, the structural resemblances between Amphioxus and the Asci- 

 dians had been pointed out by Goodsir ; and Kowalevsky in 18GG 

 showed that these were not mere analogies, but indicated a real 

 affinity. These observations, in the words of Allen Thomson, ' have pro- 

 duced a change little short of revolutionary in embryological and zoolo- 

 gical views, leading as they do to the support of the hypothesis that the 

 Ascidian is an earlier stage in the phylogenetic history of the mammal 

 and other vertebrates.' 



The larval forms which occur in so many groups, and of which the 

 Insects afford us the most familiar examples, are, in the words of 

 Quatrefages, embryos, which lead an independent life. In such cases as 

 these external conditions act upon the larvas as they do upon the mature 

 form ; hence we have two classes of changes, adaptational or adaptive, 

 and developmental. These and many other facts must be taken into 

 consideration ; nevertheless naturalists are now generally agreed that em- 

 bryological characters are of high value as guides in classification, and 

 it may, I think, be regarded as well-established that, just as the con- 

 tents and sequence of rocks teach us the past history of the earth, so is 

 the gradual development of the species indicated by the structure of the 

 embryo and its developmental changes. 



When the supporters of Darwin are told that his theory is in- 

 credible, they may fairly ask why it is impossible that a species in the 

 course of hundreds of thousands of years should have passed through 

 changes "which occupy only a few days or weeks in the life-history of 

 each individual ? 



The phenomena of yolk-segmentation, first observed by Prevost and 

 Dumas, are now known to be, in some form or other, invariably the pre- 

 cursors of embryonic development ; while they reproduce, as the first 

 stages in the formation of the higher animals, the main and essential 

 features in the life-history of the lowest forms. The 'blastoderm,' as 

 it is called, or first germ of the embryo in the egg, divides itself into 

 two layers, corresponding, as Huxley has shown, to the two layers into 

 which the body of the Ccelenterata may be divided. Not only so, but 

 most embryos at an early stage of development have the form of a cup, 

 the walls of which are formed by the two layers of the blastoderm. 

 Kowalevsky was the first to show the prevalence of this embryonic 

 form, and subsequently Laukester and Hasckel put forward the hypo- 



