ANIMAL KINGDOM. 285 



true saltus in nature, when on looking at the Coleopte- 

 rous insects generally, and on dividing them into five na- 

 tural groups taken from their general appearance, and 

 their manner of living, I endeavoured to discover some 

 distinct character for each. For some time I failed in the 

 object of my wishes ; but Bonnet's unsuccessful attempt 

 to arrange insects by their larvae happening to occur 

 to me, I perceived on examining my groups that the 

 larvse of all of them were very distinct from each other 

 in point of appearance. Of the fifth group indeed I could 

 form but little judgement, as the larvse of it were but very 

 imperfectly known ; but in the other four were to be 

 discerned Scolopendriform larva?, Juliform larvae, Apod or 

 Vermiform larvse, and active Hexapod larva?. The ana- 

 logy was evident; and I was thus immediately led to con- 

 clude that there was an error in the degree of importance 

 which in the above classical division of the Annulosa had 

 been given to the Vermes. 



M . Rudolphi in his excellent work on the JEnlozoa found 

 it necessary to make two great sections of them, which 

 have by succeeding writers been elevated to the rank of 

 classes on account of the vast difference between their re- 

 spective organizations. Now, that when thus contrasted 

 With one another they ought to form separate classes will 

 not admit of doubt, as we shall see by the following state- 

 ment. One of these sections is composed of intestinal 

 worms without any distinct organs, animals whose exist- 

 ence is only proved by the irritability of their soft vesicu- 

 lar substance. The other on the contrary consists of such 

 as are furnished with a nervous system formed by two 

 longitudinal threads terminating in a medullary collar, — 

 worms, in short, which have two apertures to their in- 



