170 HIXTS ON THE ANCESTRY OF INSECTS. 



possible that one of these creatures may have given rise to a 

 form resulting in two series of beings, one leading to the Lep- 

 tus form, the other to the Nauplius, For the true Annelides 

 (ChaBtopods) are too circumscribed and. homogeneous a group 

 to allow us to look to them for the ancestral forms of insects. 

 But that the insects may have descended from some low worms 

 is not improbable when we reflect that the Syllis and allied 

 genera of Annelides bear appendages consisting of numerous 

 joints; indeed, the strange Dujardiuia rotifera, figured by Qua- 

 trefages, in its general form is remarkably like the larva of 



Chloeon. It has a quite distinct 

 I head, bearing five long, slender, 

 jointed antennae, and but eight or 

 I nine rings to the body, which ends 

 in two long, many jointed appen- 

 dages exactly like the tentacles. 

 Quatrefages adds, that its move- 

 Iments are usually slow, but "when 

 it wishes to move more rapidly, it 

 moves its body alternately up and 

 down with much vivacity, and 

 shoots forwards by bounds, so to 

 speak, a little after the manner of 

 the larvae of the mosquito" (His- 

 |toire Naturelle des Anneles,Tome 

 p. 69), The gills of aquatic 

 [insects only difler from those of 

 worms in possessing tracheae, 

 198. A Rotifer. though the gills of the Crustacea 



may be directly compared with those of insects. 



But when once inside the circle of the class of insects the 

 ground is firmer, as our knowledge is surer. Granting now that 

 the Leptus-like ancestor of the six-footed insects has become 

 established, it is not so difficult to see how the Podurae and 

 finally a form like Campodea appeared. Aquatic forms resem- 

 bling the larva of the Ephemerae, Perlae and, more remotely, 

 the Forficulae and white ants of to-day were probably evolved 

 with comparative suddenness. Given the evolution of forms 

 like the earwigs (Forflcula), cockroaches and white ants (Ter- 

 mes), the latter of which abounded in the coal period, and it 

 was not a great step forward to the evolution of the Dragon- 



