120 HISTORY OF CRUSTACEA. CHAP. XL 



Which of the different modes of development at 

 present occurring in a class of animals may claim to be 



investigation can demonstrate the mutual relationships of Termes, 

 Blatta, Mantis, Forficula, Ephemera, Libellula, &c. I may refer to 

 a corresponding remarkable example from the vegetable world : amongst 

 Ferns the genera Aneimia, Schizxa and Lygodlum, belonging to the 

 group Schizxacex which is very poor in species, differ much more from 

 each other than any two forms of the group Polypodiacex which 

 numbers its thousands of species. 



If, from all this, it seems right to regard the Orthoptera as the order 

 of Insects approaching most nearly to the common primitive form, we 

 must also expect that their mode of development will agree better with 

 that of the primitive form, than, for example, that of the Lepidoptera, in 

 the same way that some of the Prawns (Peneus) approaching most closely 

 the primitive form of the Decapoda, have most truly preserved their 

 original mode of development. Now, the majority of the Orthoptera 

 quit the egg in a form which is distinguished from that of the adult 

 Insect almost solely by the want of wings ; these larvae then soon 

 acquire rudiments of wings, which appear more strongly developed 

 after every moult. Even this perfectly gradual transition from the 

 youngest larva to the sexually mature Insect, preserves in a far higher 

 degree the picture of an original mode of development, than does the 

 so-called complete metamorphosis of the Coleoptera, Lepidoptera, or 

 Diptera, with its abruptly separated larva-, pupa- and imago-states. 



The most ancient Insects would probably have most resembled these 

 wingless larvae of the existing Orthoptera. The circumstance that there 

 are still numerous wingless species among the Orthoptera, and that 

 some of these (Blattidse) are so like certain Crustacea (Isopods) in 

 habit that both are indicated by the same name (" Baratta "; by 

 the people in this country, can scarcely be regarded as of any im- 

 portance. 



The contrary supposition that the oldest Insects possessed a " com- 

 plete metamorphosis," and that the " incomplete metamorphosis " of the 

 Orthoptera and Hemiptera is only of later origin, is met by serious 

 difficulties. If all the classes of Arthropoda (Crustacea, Insecta, 

 Myriopoda and Arachnida) are indeed all branches of a common stem 

 (and of this there can scarcely be a doubt), it is evident that the water- 

 inhabiting and water-breathing Crustacea must be regarded as the 

 original stem from which the other terrestrial classes, with their 

 tracheal respiration, have branched off. But nowhere among the 

 Crustacea is there a mode of development comparable to the "complete 

 metamorphosis" of the Insecta, nowhere among the young or adult 



