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science to which the attention of scientific entomologists has been 

 directed of late years, and first as to the subject of "Classification." 

 The matter of classification naturally deals with the relationship that 

 insects bear (i) to each other and (2) to all other animals. The 

 animal kingdom is primarily divided into two great sections (1) 

 the Protozoa (or one-celled animals); (2) the Metazoa (or many- 

 celled animals). In the latter the cells are generally built up into 

 tissues, and the tissues arranged in three fundamental layers — the 

 ectoderm (outer layer), the mesoderm (middle layer), the endoderm 

 (inner layer). The vast assemblage of animals included in the 

 Metazoa are subdivided into several main groups or phyla, of which 

 the chief are the Porifera (sponges), the Ccelenterata (sea-anemones, 

 jelly-fishes, &c), Vermes (worms), the Echinodermata (sea-urchins, 

 star-fishes, &c), Mollusca (snails, mussels, &x.), the Arthropoda 

 (crustaceans, insects, &c), and the Vertebrata (ascidians and fishes 

 to man). The insects belong to that phylum termed Arthropoda, so 

 that the nearest allies to insects, i. <?., those belonging to the same 

 phylum, include the Arachnida (spiders), Crustacea (lobsters, crabs, 

 &c), and the extinct Trilobites. 



It is generally conceded by all naturalists that insects stand at the 

 head of the Arthropoda. Their bodies are complicated in structure, 

 and their organs more specialised in the adult stage than those of any 

 other class belonging to this particular phylum. There can be 

 no doubt that the power of flight has led to the great success of 

 insects in the struggle for existence, and that their ability to move 

 rapidly has been the basis of their success in escaping from their 

 numberless enemies, and the proximate cause of their numerical 

 superiority in genera and species. For a similar reason probably — 

 viz. the power of moving through the water rapidly — fishes owe their 

 success over animals that lead an aquatic life. 



The Arthropods as a whole are characterised by the body being 

 made up of segments bearing jointed appendages. The segmeirs, 

 too, are more or less clearly divisible into a cephalothorax and 

 abdomen, by which characters they are separated from the Annelid 

 worms. In their internal organs, however, the general character and 

 arrangement of the organs, the position and general shape of the 

 alimentary canal, of the nervous and circulatory sy.-^tems, agree 

 broadly with those of the Annelid worms, so much so that many 

 naturalists trace the descent of the Arthropods from the worms ; 

 others, however, prefer the much safer theory that the two have 

 descended from a common ancestor which possessed the main 

 characters now common to both these groups. As a matter of fact 

 the Arthropod phylum contains within ii self such important sub- 

 divisions that it is possible it comprises the elements of at least three 

 or four other phyla. Many eminent entomologists have discussed 

 the origin of insects within the Arthropod phylum. 



We have no further time at our disposal than to state that by 

 their structure, metamorphoses, and embryology, the Myriapoda and 



