LIST OF ENTOMOLOGICAL WORKS. 293 



Newman, in a paper read before the Linnaean Society of 

 London, and lately published in this Magazine, 3 has shown 

 most clearly, that the metamorphosis of insects is nothing 

 more than ecclysis, or a sloughing of the external covering. It 

 is perfectly true, that ecdysis occasionally takes place with 

 little or no alteration of external form ; it is true also, that in 

 metamorphosis a complete change of external forms frequently 

 takes place ; but it is equally true, that we are acquainted with 

 every degree in the graduated scale between the maximum 

 and minimum degree of change. Under these circumstances, 

 we are compelled to acknowledge that metamorphosis is 

 ecdysis, and that ecdysis is metamorphosis ; for the mind 

 refuses to apply one reasoning to any given portion of a series, 

 and seek another reasoning for a different portion of the same 

 series. 



There is no subject which has caused so great a sensation 

 among Naturalists as the metamorphosis of Decapods. For 

 this highly important discovery we are indebted to Mr. 

 Thompson. He has shown, beyond the possibility of dispute, 

 that Decapods commence their existence under a form widely 

 differing from that in which they arrive at maturity. Bosc, in 

 his "Histoire Naturelle des Crustaces," has named, described, 

 and figured, a minute oceanic insect, under the name of Zo'ea 

 pelagica. h Latreille altered the name to Zoe, in his " Genera 

 Crustaceorum et Insectorum ;" c and Leach, in the " Edinburgh 

 Encyclopaedia," d and " Encyclopaedia Britannica," e adopts the 

 latter name, and describes the insect. This same Zoe is now 

 proved to be the state of a crab, or some Decapod, imme- 

 diately on its exclusion from the ovum. Another genus, 

 named Megalopa by Leach, and not hitherto supposed to be 

 related to Zoe, proves also to be a young crab advanced 

 another stage towards perfection ; but it appears that more 

 than one ecdysis is necessary to convert a Zoe into a Mega- 

 lopa, and probably several more to convert a Megalopa into 

 a crab. The very recent date of these important discoveries 

 clearly shows how much we are still in the dark as to the value 

 of our genera of Crustacea, and how completely we stand 

 in need of a complete revision of our classification in this branch 

 of Entomology. Sincerely do we hope that Mr. Thompson 



a See page 12 of the present volume. b Tom. II. p. 185, pi. 15, f. 3,4. 



c Tom. I. p. 21. d VII. 889. e Suppl. I. 423. 



