266 ANNUAL OF SCIENTIFIC DISCOVERY. 



to permanence, depend on the comparative development of differ- 

 ent elements of a common plan ; from which it seems to follow 

 both that the non-existence from the commencement of living 

 nature of all the distinct plans of structure is in the highest degree 

 improbable, and that the tendency of development, sometimes in 

 one direction, sometimes in another, among the same primitive 

 elements, must produce a harmonious S} T stem ; whilst the preser- 

 vation of the forms best adapted to a situation amongst a great 

 number of variations arising without order must produce a con- 

 fused mass of objects having no regular relations and incapable 

 of being reduced to a common system. Which of these prevails 

 in nature, I cannnot for a moment hesitate in deciding, and conse- 

 quently I must maintain that, if there is variation, it must be 

 within definite limits, and according to a fixed plan, so as to 

 maintain a uniform order and harmony in the whole system." 

 Nature. 



SPONTANEOUS GENERATION. 



Spontaneous generation, or heterogeny, is a question which 

 continues to excite much interest. It has been the subject of de- 

 tailed memoirs, of violent controversies, and of popular articles 

 in this country, and still more on the Continent; but the solution 

 of the problems still involved in doubt does not seem to me to 

 have much advanced since I alluded to the opposing theories of 

 Pasteur and Pouchet in my Address of 1863. The present state 

 of the case appears to me to be this : in the higher orders of ani- 

 mals every individual is known to proceed from a similar parent 

 after sexual pairing ; in most plants, and some of the lower ani- 

 mals, besides the result of that sexual pairing which they all are 

 endowed with, reproduction from the parent may take place by 

 the separation of buds, by division, or sometimes by parthenoge- 

 nesis; in some of the lower Cryptogams, the first stage in which 

 the new beings are separated from the parent is that of spores 

 termed organic, from the belief that they never require previous 

 sexual pairing, although the range of these agamic races is being 

 gradually restricted, a remarkable advance having been recently 

 made in this direction by Pringsheim in his paper on the pairing 

 of the Zoospores in Pandorina and Eudorina. In all the above 

 cases, in all organized beings which, in their earlier stages, are 



* ^j ^j ' ^j 



appreciable through our instruments, every individual has been 

 proved to have proceeded in some stage or another from a simi- 

 larly organized parent. But there are cases where living beings, 

 Vibrios, Bacteria, etc., first appear under the microscope in a 

 fully formed state, in decaying substances in which no presence 

 of a parent could be detected or supposed : three different theories 

 have been put forward to account for their presence ; first, that 

 they are suddenly created out of nothing, or out of purely inor- 

 ganic elements, which is perhaps the true meaning disguised 

 under the name of spontaneous generation, a theory not suscepti- 

 ble of argument, and therefore rejected by most naturalists as 

 absurd ; secondly, that they are the result of the transformation 



