70 HUMBiE CREATURES. 



lineated in fig. 5; or when' fully extended, as at 

 fig. 6. 



On the posterior portion of the last ring (fig. 1 a, 13), 

 as well as at the side of every other segment of the 

 larva, are to be found spiracles or respiratory holes 

 symmetrically disposed in pairs ; and within the body 

 may be seen a very perfect system of trachese or 

 respiratory tubes, two or three of which are visible 

 in fig. 6, t, and which serve to aerate the circulating 

 fluid. 



With the exception of these organs the larva 

 presents the appearance of a smooth Worm, void of 

 members of any kind ; but when the microscope is 

 brought to bear in its examination, it is found to be 

 covered vrith a vast number of diminutive hooks, 

 disposed in regular rows or circlets upon each ring 

 (PI. VIII. figs. 1 «, 5 & 6), which remind us forcibly 

 of the hooks upon the body of the worm, and thus 

 render the analogy between the two living objects still 

 more remarkable. 



Whilst in this state, the larva is constantly de- 

 vouring the substances in which it was hatched, and 

 increases rapidly in size ; it is, however, asexual, i. e. 

 incapable of reproduction, and in a few days assumes 

 the pupa-form. This change is elFected by the 

 hardening of the outer skin, which becomes brown 

 and tough, inclosing the larva in a little bright 

 barrel-shaped case, divided into rings or segments 

 (PI. VIII. fig. 2), and it is then to all appearance 

 lifeless. 



