address. lxxiii 



and animals existing on the earth's surface derive their origin from parents 

 or previously existing heings vrhose form and nature they closely reproduce 

 in their life's history. By far the greater number spring from germs in tho 

 form of visible and known spores, seeds, or eggs ; a few may be traced to 

 other germs, or to vestiges of the parental body, the exact nature of which 

 may be doubtful ; and some, including even a certain number of those also 

 produced from known germs, are either constantly or occasionally multiplied 

 by budding, or by a process of cleavage or direct and visible division of tho 

 parent body. 



The germ constituting the basis of new formation, whether it be of un- 

 known nature or in 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 

 complex form and structure : it is one of " evolution " or, more appropriately 

 named, of " development." But before proceeding to discuss the subject of de- 

 velopment in beings of which the germs are known, it is right to advert to the 

 preliminary and often debated question, which naturally presents itself, viz.: — 

 Do all living or organized beings, without exception, spring from germs, or 

 from any kind of organized matter that has belonged to parents? or may 

 there not be some, especially among the simpler forms (with regard, indeed, 

 to which alone there has of late been any question), which are produced by the 

 direct combination of their component elements, in the way of the so-called 

 spontaneous or equivocal generation, heterogenesis or abiogenesis ? 



The importance of the right solution of this problem is not confined 

 merely to the discovery of the mode of origin of the lowly organisms which 

 have been the more immediate object of investigation by naturalists in recent 

 times, but is one of much wider significance, seeing that, if it shall be satis- 

 factorily proved or even rendered probable that in the course of cosmical 

 development all the various kinds of plants and animals have been gradually 

 produced by evolution out of preexisting simpler forms, and thus the whole 

 series of organized beiugs in nature is shown to be one of hereditary con- 

 nexion and derivation, then it would follow that the history of the origin of 

 the simplest organisms may be the key to that of the first commencement of 

 life upon the earth's surface, and an indication of the relation in which 

 the whole succeeding progenies stand to their parental stocks. 



From the very lucid and masterly view of this subject given by Prof. Hux- 

 ley in his Address to the Association at Liverpool, so recently as in IS 70, 

 in which the conclusion he formed was mainly based on the exhaustive 

 and admirable researches of Pasteur, I might have dispensed with making 

 further reference to it now, but for the very confident statements since made 

 by the supporters of the doctrine of Abiogenesis, among whom Dr. Bastian 

 stands most prominent in this country, and for the circumstance that the 

 life-history of many of the lower organisms was still imperfectly known. 



