On the sixty-third day the Joins again changed its skin, and entered its sixth period of developement (fig. 326). It then had ac quired twenty-seven segments to its body, which had greatly increased in size and was of a brown colour. It had now six distinct ocelli on each side of the head, and all the segments to the eighteenth inclusive were furnished with legs, of which it had now fifty-eight. Six addi tional new segments had also been developed to its body. as in the preceding changes anterior to the penultimate segment (1 g h 1 2 3 4 5 6), and the germinal membrane behind them (i) was still in further course of developement, the penultimate segment (26) remaining always unchanged. The six segments (28) from which legs had been developed had also the fbramina repugnaloria marked with small spots, while the spots on the preceding six had become larger and darker in colour, and the animal might now be regarded as having acquired all the essential parts of its body, its subsequent growth doubtless being effected by a repetition of the same interesting phenomena.
The observations of Monsieur Gervais rela tive to the developement of the Scolopendroid Myriapoda, are the only ones on record with which we are acquainted ; and although these are extremely desultory and incomplete when compared with the masterly researches of Mr. Newport concerning the Jul idx, detailed above, they seem to shew that the changes under gone by the Scolopendridw, before they arrive at maturity, are scarcely less important than those we have been considering. M. Gervais studied more particularly the growth of Litho bins, 309,) Scolopendrw, which possess, when mature, fifteen pairs of feet, and also some individuals belonging to the genus Geophilus. A young Lithobius captured in the month of May was found as yet to possess only seven pairs of feet, ten segments in its body, two eyes on each side of its head, and but eight joints in its antenna: Moreover, that only one segment, the anal, was deprived of feet, a cir cumstance which at once forms a remarkable difference between the young Lithobii and the young Juli, which latter have several apodal segments at the posterior extremity of the body. By the eighth of June the same Litho bins had fourteen joints in the antenntv, and eight pairs of legs, to-,-,ether with eleven seg ments to its body, including an apodal one for the anal segment.
Another Lithobius of nearly the same age had already three eyes on each side, and a third only ten pairs of feet, of which the two poste rior were still rudimentary and scarcely formed.
In another example, even when all the fifteen legs were present, the creature had not as yet got its full complement of eyes, there being only eight stemmata on each side, whilst in the adult animal the optic facets are numerous.
It appears manifest, therefore, that the Li thobii, like the Juli, have the number of their segments increased as well as of their legs, and of the joints of their antenna; and, moreover, that the number of their eyes increases with their age, a remarkable fact, which M. Gervais seems to have been the first to signalize.
With respect to the manner in which the number of pairs of feet and of segments is in creased as the young Lithobius grows older. M. Gervais gives us the following infor mation : " Examined upon the ventral surface of the body, the pedigerous segments of an adult Lithobius are found to be nearly of size equal, but examined from above where they are, as it were, imbricated, some appear larger and others smaller. The largest of the pedigerous segments are the 1st, 3d, 5th, 7th, 8th, 10th, 12th, 13th, and 14th, the three last corresponding inferiorly to four half seg ments, and consequently to four pairs of feet. The 2d, 4th, 6th, 9th, and 1 lth, are smaller, and feet already exist upon these smallest seg ments even before the dorsal portion is deve loped, so that what is permanently observable in one of the posterior segments, which has superiorly only one shield, obtains also at this period for two of the posterior segments, which have as yet but one dorsal plate, the smaller of the two dorsal plates not having as yet made its appearance. This fact is remarkable, for if we suppose the same phenomenon to be con stant with all the rings, it is easy to explain how at all ages there are fewer dorsal segments than there are pairs of feet." As relates to the Geophili, M. Gervais as sures us the process is, in them, altogether changed, another proof of the numerous diffe rences met with in the physiology of the various genera of the class under consideration, but not having completed his researches upon this subject, the author of the memoir from which we have quoted has not as yet informed us of the result of his observations concerning the Geophi lid m.