ARTICULATED ANIMALS. 



405 



tliem, with certain worms, into a class, for which lie 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 b}' 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 Anojjlura ; to unite the 

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

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

 to Aludeni Classijic. 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 projjerly the foot, is composed 

 of a series of small joints, which touch the ground, and which are 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. 



These creatures are always furnished with eyes. These are of two kinds : — 1 st, The 

 simple eyes, named ocelli, or stemmata, ordinarily resembhng 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 number of 



s otnl.ii 



* The sericK of [external] articuliiti 

 jn.sed li;is been enmiii.n il to a skeletoti, orvertulj 

 is erroneous, because the supposed vertebra- un 

 lions of tlic skin, eoniiceted by ninre slender mem 

 portions. The researches of Strauss especially pi 

 tinn to Robine 

 especially distiinruishes these from oth 



the body is com- 

 ;olumn ; but this 

 ly hardened per- 

 ilous intervening 

 this, in oppnsi- 



Tlie power of evuviation 



ivertet)rata. 



net class 



The 



t Dr. Leach formed the Myriapoda into 

 Chean .\racbnida miyhl also, from tlicir anatomical characters, consti- 

 tute another, but they are too nearly allied to the polmooary Arach- 

 nida to allow this separation. 



c feet are the Apiropoda of 



of the cova appears to form 

 in the Arachnida) are two- 



I ne.-iupods. Tliose with more thai 

 Savijiiiy, or my Hyperhc.xajiods. 



§ 111 many (_ruslaeea, the second pic 

 part of the femur, and the tibia; [us al 

 jointed. 



II According to HI. Odier, tlie chief snbstanee of which this intctjn- 

 ineiit is composed is of a pcenliar uaCiire, which lie names chitioe. 

 Phosphate of lime forms the chief part of the salts of the teguments 

 of insects, whilst the carapas of the crabs abounds in carbooatc of 

 lime. 



