MYRIAPODA. 



559 



membrane, soon to be exposed by another 

 change of skin that was about to take place. 

 The Julus ceased to eat, became torpid, 

 and lay coiled up in a spiral form. The 

 tegument of the body began to assume a 

 whitish crustaceous appearance, and the ani- 

 mals secreted themselves beneath any dry co- 

 vering, but avoided parts too wet. The princi- 

 pal changes in their general appearance were in 

 the eyes, each ocellus being much more dis- 

 tinct, and in the germinal space, which was 

 developed to its greatest extent, and distinctly 

 exhibited the six new segments. 



The change of skin, according to Mr. New- 

 port, is effected in the following manner. The 

 young Julus, when about to cast its integu- 

 ment, bends its body in a semicircular form, 

 with its head inflected against the under sur- 

 face of the second segment. In this condition 

 it remains for several hours with its legs widely 

 separated and the dorsal surface of the segments 

 extended. The head is then more forcibly 

 bent on the sternum, and a longitudinal fissure 

 takes place in the middle of the epicranium, 

 and is immediately extended outwards on each 

 side posteriorly to the antennae in the course of 

 other sutures, the analogues of which Mr. 

 Newport has described as the triangular and 

 epicranial sutures. Through the opening thus 

 formed in its covering the head is then carefully 

 withdrawn, and with it the antennse and parts 

 of the mouth, and afterwards the anterior seg- 

 ments and single pairs of legs. The first and 

 apparently the most difficult part of the shed- 

 ding of the skin is its detachment from the 

 posterior segments of the body and from the 

 interior of the colon. To effect this the ani- 

 mal, which has been previously lying coiled up 

 in a circular form, first straightens its whole 

 body ; it then forcibly contracts and shortens 

 itself, especially at the posterior part, and by 

 this means becomes greatly enlarged in bulk 

 at its middle portion, but smaller at its extre- 

 mities. During these efforts, which are some 

 of the most powerful it is able to make, the 

 skin becomes loosened from its posterior parts, 

 and while still contracting its segments, the 

 anal extremity, and with it the entire lining of the 

 colon, become completely detached, and from 

 these it gently withdraws itself within the old 

 skin in which the body is encased as from the 

 finger of a glove. This is precisely what takes 

 place in the shifting of the skin in insects. 

 Having effected this part of its labour all the 

 posterior segments are again shortened ; the 

 animal once more disposes itself in a circular 

 form, and after repeated exertions succeeds in 

 bursting the tegument of the head in the part 

 just described. As in the case of true insects 

 the young Julus entirely empties the alimentary 

 canal by voiding its faces and ceasing to eat 

 for one or two days preparatory to undergoing 

 each transformation. When examined imme- 

 diately before the change there are no other 

 symptoms of new legs than slight elevations of 

 the skin, and this perhaps accounts for the 

 length of time occupied in the change, the new 

 legs requiring time for further developement 

 before the old skin is thrown off. 



Having cast its skin and thus attained the 



fifth period of developement, the young Ju- 

 lus (fig. 325) has three ocelli on each side 



Fig. 325. 



Fig. 326. 



of the head, seven 

 joints to the antennas, is 

 thirty-four legs, and 

 twenty-one segments 

 to its body. On the 

 forty-eighth day this 

 has been accomplished, 

 and the young Ju- 

 lus exhibits a marked 

 alteration in its ap- 

 pearance. The an- 

 tennae are considerably 

 longer than the head, 

 with seven distinct 

 joints, and, as in the adult, the apical one 

 is short and inserted into the sixth. The single 

 eye has disappeared, and in its stead three 

 distinct ocelli, arranged in a triangle, have 

 been developed. The new segments of the 

 body produced at the former change of the 

 animal, from the eighth to the twelfth in- 

 clusive, (8-12,) are now of the same size as 

 the original ones, and each has developed 

 from it two additional pairs of legs, so that 

 the whole number of legs is now thirty-four. 

 The thirteenth, or, if we may so name it, 

 germinal segment of the last period, is less de- 

 veloped than the preceding ones, and is distin- 

 guished from them by the circumstances that it 

 is smaller, possesses no legs, and has no lateral 



