52 
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, &e., 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 (luring its 
whole life: at first without wings; 
acquires rudiments of them in the 
nymph, and they become complete 
in the imago. Neuroptera , Orthop- 
tera , Hemiptera. 
h. 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 seme 
other tribes of animals related to insects, may almost 
