ARTICULATED ANIMALS. 



•105 



them, with certain worms, into a class, for which he adopted Leach's name, Ameta- 

 bola (changeless), in order to distinguish them from the true insects, which undergo 

 transformations. This author retained the classes Crustacea and Arachnida, but di- 

 vided the insects, from the structure of their mouth-organs, into those with mandibles 

 and those with a suctorial mouth, — characters which we have seen had been employed 

 in the arrangement of the orders of insects inter se. 



Other arrangements have been proposed by Kirby and Spence, Burmeister, &c, to 

 which I can but refer. — I shall, therefore, only add that it appears to me most natural 

 to confine the Ametabola to the Myriapoda, Thysanura, and Anoplura; to unite the 

 winged insects into one class, named Ptilota, after Aristotle ; and to retain the Crustacea 

 and Arachnida in the limits here detailed. — Entomol. Text-Book, p. 79 ; and Introd. 

 to Modern Classific, of Insects, vol. i. p. 4.] 



ARTICULATED ANIMALS, FURNISHED WITH ARTICULATED FEET,* 



IN GENERAL. 



CRUSTACEA, ARACHNIDA, AND INSECTA. 



These threef classes, united together by Linnaeus under the common name of Insects, 

 but which I name Condylopa, are distinguished by their articulated feet, of which they 

 have at least six.} Each joint [of the legs] is tubular, and contains the muscles of the 

 following articulation, which always moves by ginglymus, — that is, in but one direc- 

 tion. The first joint which attaches the limb to the body, and which is generally com- 

 posed of two§ pieces, is named the coxa, or hip, [the second of these pieces, when 

 present, is termed the trochanter] ; the next piece, which is ordinarily in a position 

 nearly horizontal, is the femur, or thigh ; the third is generally vertical, and is named 

 the tibia, or shank ; and the terminal part of the leg, or properly the foot, is composed 

 of a series of small joints, which touch the ground, and which arc collectively named 

 the tarsus. 



The hardness of the calcareous or horny || envelope of the majority of these animals 

 is owing to that of the excretion which is interposed between the dermis and epidermis, 

 or what is termed in Man the mucous tissue. It is also in this excretion that are lodged 

 the often brilliant and varying colours with which these animals are sometimes adorned. 



Th- se creatures are always furnished with eves. These are of two kinds : — 1st. The 

 Bimpleeyes, named ocelli, or stemmata, ordinarily resembling a minute' lens, and of which 

 there are generally three', arranged in a triangle on the crown of the' head; and. 2ndly, 

 the facetted or composite eyes, of which the surface' is divided into an infinite Dumber of 



• The seriei of [ejternal] arliculatloni of which Ihi body ll com- 



Itoaahalati r rartebral cohmui i bat thla 



li anmMu, btaui the rappoaad rartabn u t -,i ,„. r - 



i ton ilandei membruou InUrm Ding 

 l""""'' ' ■ oppnal- 



1 '" RoblntM Dearoldr, ud othtra. 1 1,, power ..I rxurUUon 



eupcciilljr dlailnirulahaa th. -r rram othn Inrorubrat*. 

 | Dr. Leach formed th ' Into a dlatlnct claaa. Their*- 



roa tii.-ir anatomical chanctan, 



tulc another. I.ul Ihl7 »re (,>o nearly allied lu the pulmonary 

 nida to allow thla ■•para) 



1 HempotU. Tho.e with more than nx feet are the 



. or my Ilypi rti. \ a| 



J In many Croatacaa, lha lacond pit v* appear, t 



part of tlit femur, and (lie tibia (aa al»o in the Araehio 



I According to M. Odlar, tht f which thla Inl 



inrnt i-. com] 'I i* of a pr.ulitr nature, which tie name, i Inline. 



PhOa| hate of lime form, tin- i hut |>.»rt ,.( ibf %ilt. ..t the le k -umeiita 

 of imtrcti, whllal the carapal of the crr.bt abouda in carbonate of 



