152 



HINTS OX THE ANCESTRY OF INSECTS. 



Who can explain the origin of the sexes? What is the cause 

 tliat determiues that one individual in a brood of Stylops, for 

 example (Fig. 184, male; Fig. 185, grub-like female in the body 

 of its host), shall be but a grub, living as a parasite in the 

 body of its host, while its fellow shall be winged and as free iu 

 its actions as the most highly organized insect? It is no less 

 mysterious, because it daily occurs before our eyes. So perhaps 

 none the less mysterious, and no more discoi'dant with known 

 natural laws may the law that governs the origin of species 

 seem to those who come after us. Certainly the present 

 attempts to discover that law, however fatuitous they may 

 seem to many, are neither illogical, nor, judging by the impetus 



alread}' given to biology, or the 

 science of life, labor altogether 

 spent in vain. Tlie theory of 

 evolution is a powerful tool, 

 when judiciously used, that must 

 eventually wrest many a secret 

 from the grasp of nature. 



But whether true or unproved, 

 the theory of evolution in some 

 shape has actually been adopted 

 by the large proportion of natu- 

 ralists, who tind it indispensable 

 in their researches, and it will be 

 used until found inadequate to 

 explain fiicts. Notwithstanding 

 the present distrust, and even 

 185. Female Stylops. fear, with which it is received 



by many, Ave doubt not but that in comparatively few years all 

 will acknowledge that the theory of evolution will be to biology 

 what the nebular hypothesis is to geology, or the atomic theory 

 is to chemistry. While the evolution theory is as yet imperfect, 

 and many objections, some seemingly insuperable, can be raised 

 against it, it should be borne in mind that the nebular hypoth- 

 esis is still comparatively crude and unsatisfactory, though 

 indispensable as a working theory to the geologist; and in 

 chemistry, though the atomic theory may not be satisfactorily 

 demonstrated to some minds until an atom is actually brought 

 to sight, it is yet invaltiable in research. 

 Many short sighted persons complain that such a theory sets 



