241 



drying of the matter and the volatility of the oil, will be shown by the following ob- 

 servations. Julus pulchellus dwells in very moist spots, often where the decayed ve- 

 getable matter is becoming quite fluid, and it seems not to suffer from being kept for 

 twenty-four hours at the bottom of a tumbler of water. The other species live in more 

 dry habitations, and they have the colour and scent which Julus pulchellus acquires 

 only after death, for it is quite inodorous during life. When Julus pulchellus is 

 plunged into hot water, its colour changes immediately to intense violet blact, but 

 when it is killed by spirits of wine or brimstone, the blackness comes on gradually and 

 continues to increase till some few days are past. The oil exudes from the body when 

 the insect is touched and when it is dead, and spreads over the surface whereon it is 

 placed. When a number are killed, dried and ground in a little water, the latter be- 

 comes black, and in a few days changes first to brown, then to yellow, and acquires a 

 strong fetid odour. When it crawls, its legs form about seven waves at once. Its bo- 

 dy is full of soft pulpy matter, but the greater part of the larger species is dry and 

 empty immediately after death, the muscles adhering to the inside of the segments. 

 The four segments adjoining the head and the five anal segments are unspotted, and 

 are the last to acquire the black colour. The spots are pear-shaped, and the crimson 

 fluid often escapes from them when the creature is injured, and being suffused over 

 the body give it the apearance of a bright red worm. It is most smooth when young, 

 but afterwards the striae are more deeply marked. In its very early state the thorax 

 comprises half the length of the body, and the abdomen has but two segments, but 

 more are successively added, and the capacity for food is increased till there are fifty, 

 nearly all foiining part of the abdomen. 



It is a law of anatomy that each organ has at first an almost imperceptible appear- 

 ance, then attains its maximum of development, and finally dwindles away and disap- 

 pears from the scene of action ; and accordingly the minuteness of the tracheae of 

 Chilognatha prefigures their cessation and the introduction of a new system of respi- 

 ration, as we find takes place in the neighbouring classes of Crustacea and Annelida. 

 Julus has much affinity to the latter, and we will notice the earth-worm (Lombricus), 

 and mention some of the external characters in which it and Julus differ. All the 

 segments of Lombricus serve for locomotion, which is effected by their extending and 

 contracting alternately. Julus, by the process which is variously called shortening the 

 axis and elaborating the organs or developing the superior pole, acquires a head, com- 

 prising eyes, antennae, labium and mandibles, which are by some supposed to be the 

 higher structure of so many segments or vertebrae. Thus some few of the segments 

 that serve the Lombricus to glide ajong under ground, are in the Julus converted into 

 organs of gnawing, seeing, feeling, and probably of other senses. The segments of 

 Lombricus are altogether membranaceous and are sometimes striated longitudinally, 

 those of Julus are also usually striated but are mostly coriaceous, having however a 

 soft membranous part between each ; they do not in themselves serve for moving from 

 place to place, this is effected by the legs, pair after pair of which, with the vertebrae 

 that bear them, successively appear between the antepenultimate and penultimate seg- 

 ments. Thus, though the metamorphose of Julus begins at the superior pole, yet it 

 is mostly carried on by the inferior pole, and accordingly consists in the development 

 of functions exercised by that part of the body. Each segment after the third bears 

 two pairs of legs, or, as some say, the segments are anchylosed two and two togethei-, 

 and thus one segment has, in fact, but one pair of legs. Julus and the other Chilo- 

 gnatha form a group connecting the Annelida with the Crustacea, the skin of the for- 



