$2 MEMOIR OF SWAMMERDAM. 



the investigations relating to insects, which compose 

 the greater portion of the work, there is a lengthened 

 account of the snail, {Helix,) explaining its anatomy, 

 mode of propagation, c., a treatise on the generation 

 of the frog, on the anatomy of the cuttle-fish, &c. 



The manner in which Swammerdam treats of the 

 arrangement of insects into classes, is, as might he 

 expected, not a little defective. But he was cer- 

 tainly the first that assumed metamorphosis as the 

 basis of a natural system, and in so doing, merits 

 high approbation. He referred all to four classes of 

 metamorphosis, which, translated into the modern 

 language of entomology, may be expressed as follows : 



1. No metamorphosis. The animal changes its skin, but pre- 



serves its primitive form ; as in Ara- 

 nea, Pulex, Myriapodes. In short 

 the Aptera of Linnaeus. 



2. Metamorphosis, a. Incomplete. Animal active during itd 



whole life : at first without wings ; 

 acquires rudiments of them in the 

 nymph, and they become complete 

 in the imago. Neuroptera, Orthop- 

 terdj Hemiptera. 



" b. Complete. Animal immoveable in the 



nymph state; but possessed of limbs, 

 Hymenoptera, Coleoptera, Lepidoptera. 



c. Coarctate. Animal without limbs, and 



incapable of motion in the nymph 

 state. Diptera. 



The science of insect anatomy, as well as of some, 

 ather tribes of animals related to insects, may almost 



