DEFINITION OF THE TERM INSECT. 25 



quisition of six legs, wings, a change of the oral organs 

 and of the form ; in some of the Octopods (Acarus L.), 

 in the acquisition of a pair of legs ; and in others (Pha- 

 langium and Aranea L.), solely in a modification of them 

 as to their proportions ; in the Myriapods, the alteration 

 that takes place in this respect is considerable ; a large 

 number of pairs of legs is acquired and many additional 

 abdominal segments, and the proportion which the ab- 

 domen bears to the whole insect is quite altered. In all 

 these cases there is a change more or less, either partial 

 or general, of the original shape or organs of the animal; 

 and with regard to their metamorphosis, there is a greater 

 difference between a young and adult lulus than between 

 a young and adult grasshopper or bug: so that if the meta- 

 morphosis, per se, be assumed as a principal regulator of 

 the class, the grasshopper or bug have as little claim to 

 belong to it as the lulus. 



M. Lamarck lays considerable stress upon another 

 character — That Insecta engender only once in the course 

 of their lives, and Arachnida more than once. But this, 

 if examined, will be found to be confined chiefly to the 

 Pulmonary Arachnida, the Tracheans following the law 

 of Insecta in this respect a . 



You may perhaps object that the bringing of the Tra- 

 chean Arachnida and the Myriapoda into the class In- 

 secta will render the approximation of them to a natural 

 arrangement more difficult, since it will be impossible 

 at the same time to connect the Myriapods with the 

 Crustacea, and the Trachean with the genuine Arachnida. 



a Male Insecta in some instances engender more than once. Mr. 

 MacLeay sen. has observed this with regard to Chrysomela Polygoni, 

 and I have noticed it in Bomhyx Mori 



