DEVELOPMENT OF THE FORMS OF ANIMAL LIFE. 



483 



constructed, I should have to produce a long cata- 

 logue of distinguished names, among which would 

 be found those of Lyell and Owen, as earliest 

 shaping the doctrines and guiding opinion in this 

 country ; Johannes Muller and Von Baer, as taking 

 the places of Ilaller and Cuvier on the Continent ; 

 and a host of other faithful workers in biology 

 belonging to the earlier part of this century, such 

 as those of G. Treviranus, J. F. Meckel, Cams, and 

 many more. 1 To Huxley more especially, and to 

 Herbert Spencer, the greatest influence on British 

 thought in the same direction is to be ascribed. 



Let us hope that in these times, when it has 

 been found necessary to modify the older topo- 

 logical views to so great an extent, although there 

 may still be much that is unknown, and wide 

 differences of opinion in regard to the nature and 

 sequence of natural phenomena and the mode of 

 their interpretation, all naturalists will now con- 

 cur in one important principle, viz., that truthful 

 observation and candid judgment must alone be 

 our guides in the interpretation of Nature, and that 

 that theory of creation is most deserving of our 

 adoption which is most consistent with the whole 

 body of facts carefully observed and compared. 



To attempt to trace, within the limits to which 

 my remarks must be confined, the influence which 

 the progress of knowledge has exercised upon 

 the scientific and general conception of biological 

 doctrines would be impossible, for the modifica- 

 tion of opinion on these subjects has proceeded 

 not less from the rapid advance which our age 

 has witnessed in the progress of general science, 

 especially of physics and chemistry, than from 

 that of departments belonging to biology itself. 



Thus, to go no further than the most general 

 laws of Nature, the whole doctrine of the conser- 

 vation and transmutation of force in physics, so 

 ably expounded to this xVssociation by Mr. Justice 

 Grove, the theory of compound radicals and sub- 

 stitution, with the discovery of organic synthesis, 

 in chemistry, and the more recent advance in 

 speculation with regard to the molecular consti- 

 tution and properties of matter, with which we 

 must associate the names of our last President 

 and of Clerk Maxwell, in completely changing 



1 It would also lie unjust totimit to mention here one 

 of the earliest attempts to bring British opinion into a 

 new channel, by the remarkable work entitled " Vestiges 

 ef Creation," which appeared in 1S44, or to conceal from 

 ourselves the unmerited ridicule and obloquy attempted 

 to be thrown upon the author, not perhaps so much on 

 account of the many inaccuracies unavoidable in an at- 

 tempt at the time to overtake so large a field, as directed 

 against the dangerous tendencies supposed to lurk in 

 its reasoning. 



the aspect of physical and chemical sciences 

 within the last thirty-five years, have paved the 

 way for views of the constitution and action of 

 organized bodies very different from those which 

 could be formed at the time of the first meeting 

 of the Association in this place. And if, con- 

 fining ourselves to the department of biology, we 

 add the discovery by microscopical observation 

 of the minuter elementary forms of organization, 

 more especially as flowing from the comprehen- 

 sive views of organized structure promulgated by 

 Sehleiden and Schwann nearly forty years ago, 

 the later discovery and investigation of living- 

 protoplasmic substances, the accumulated evi- 

 dence of progressive types of animal and vege- 

 table forms in the succession of superimposed 

 strata composing the crust of the earth, the re- 

 cent discoveries as to the conditions of life at 

 great depths in the ocean, the vast body of knowl- 

 edge brought together by the labors of anatomists 

 and physiologists as to the structure and func- 

 tions of almost every plant and animal, and (still 

 more, perhaps, than any other single branch of 

 biological inquiry) if we note the rapid and im- 

 mense progress which has been made during the 

 last fifty years in the study of the entirely modern 

 science of the development of living beings — we 

 shall be able to form some conception of the 

 enormous extension in our time of the basis of 

 observation and fact from which biological phe- 

 nomena may now be surveyed, and from which 

 just views may be formed as to their mutual re- 

 lations and general nature. 



It is now familiarly known that almost all (if 

 not indeed all) the plants and animals existing on 

 the earth's surface derive their origin from par- 

 ents or previously-existing beings whose form 

 and nature they closely reproduce in their life's 

 history. By far the greater number spring from 

 germs in the form of visible and known spores 

 seeds, or eggs. A few may be traced to germs, 

 or to vestiges of the parental body, the exact na- 

 ture of which may be doubtful ; and some, in- 

 cluding even a certain number of those also pro- 

 duced from known germs, are either constantly 

 or occasionally multiplied by budding, or by a 

 process of cleavage, or direct and visible division 

 of the parent body. 



The germ constituting the basis of new forma- 

 tion, whether it have the form of spore, seed, or 

 ovum, is of the simplest kind of organization, and 

 the process by which a new plant or animal is 

 produced is necessarily one of gradual change 

 and of advance from a simpler to a more com. 

 plex form of structure : it is one of " evolution," 



