RELATED BY DEGREES. 113 



degree. We have the degree of rank among animals, from the 

 lowest to the highest. There is the degree of complication in 

 their eggs. Then the degree of prevalence of budding and self- 

 division. The degree of individuality. The degrees through 

 which the higher forms pass to reach their adult state. The 

 degree of relation to the influence of secondary causes, and 

 the converse, the degree of relation to the parental influence. 

 The degree of intensity in the action of secondary causes 

 corresponding to the degree of vital power in the same species. 

 And now I will add, but not dwell upon for the present, that 

 the degree of rank in which animals have first appeared, in past 

 geological ages, is a low one for all groups. 



Thus you see all is a matter of degree,-- of progression, 

 from a lower to a higher state ; and consequently we should 

 very naturally suppose that the phenomenon of spontaneous 

 generation would make itself most conspicuous among the low- 

 est forms, when it occurred at the present day. It is not possible, 

 in the existing state of science, to say to what extent, or through 

 how many groups of animals, spontaneous generation prevails. 

 The difficulty of imitating the processes of nature, and isolating 

 them, as has been done in the case of the sealed flasks, renders 

 the multiplication of such observations a matter of exceedingly 

 slow progress. Having gone now as far as the limits will allow 

 in the investigation of the origin of the first and lowest stages 

 of life, we come next to the consideration of the relation of the 

 succeeding, more elevated phases to the latter. 

 8 



