v.J METAMORPHOSES OF INSECTS. 107 



groups ; that as Allen Thomson has truly observed, 1 

 " the occurrence of segmentation and the regularity of 

 its phenomena are so constant that we may regard it 

 as one of the best established series of facts in organic 

 nature." 



It is true that normal yolk-segmentation is not 

 universal in the animal kingdom; that there are 

 great groups in which the yolk does not divide in 

 this manner, perhaps owing to some difference in 

 its relation to the germinal vesicle, or perhaps be- 

 cause one of the suppressed stages in embryological 

 development, many examples might be given, not 

 only in zoology, but, as I may state on the authority 

 of Dr. Hooker, in botany also. But, however, this 

 may be, it is surely not uninteresting, nor without 

 significance, to find that changes which constitute 

 the life-history of the lowest creatures for the initial 

 stages even of the highest. 



Returning, in conclusion, to the immediate subject 

 of this work, I have pointed out that many beetles and 

 other insects are derived from larvae closely resembling 

 Campodea. 



Since, then, individual insects are certainly in many 

 cases developed from larvae closely resembling the 

 genus Campodea, why should it be regarded as in- 

 credible that insects as a group have gone through 

 similar stages ? That the ancestors of beetles under 

 the influence of varying external conditions, and in 

 the lapse of geological ages, should have under- 

 gone changes which the individual beetle passes 

 through under our own eyes and in the space of a few 



1 Thomson, loc. cit. Article, Ovum, p. 139. 



