560 



MYRIAPODA. 



spot which exists on each of the preceding seg- 

 ments to the seventh, marking the existence of 

 the foramina repugnatoria. The germinal 

 space (13-19) which existed in the preceding 

 period and was then seen to be forming seg- 

 ments, is now developed into six new apodal 

 segments, from the 14th to the 19th inclusive, 

 very much smaller and shorter than the rest, 

 and a germinal space (/;) is again forming be- 

 tween the last of these and the penultimate 

 segment of the body, which, as above stated, 

 undergoes no marked change. The whole 

 body is thus composed of twenty-one segments, 

 including the head. The first twelve of these 

 are now perfectly developed, as well as the last 

 two, the intermediate ones being only in their 

 preparatory states. The animals at this period 

 ate voraciously some decayed leaves, rotten 

 elm-bark, and raw potato. 



On the sixty-third day the Julus 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 () 

 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 foramina 

 repugnatoria 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 Julidge, detailed above, 

 they seem to shew that the changes under- 

 gone by the Scolopendridae, before they arrive 

 at maturity, are scarcely less important than 

 those we have been considering. M. Gervais 

 studied more particularly the growth of Litho- 

 biuK, (Jig. 309,) Scolopendrse, 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 antennae. 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- 

 bius had fourteen joints in the antenna*, and 



eight pairs of legs, together 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 antennae; 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 mferiorly to four half seg- 

 ments, and consequently to four pairs of feet. 

 The 2d, 4th, 6th, 9th, and llth, 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 

 Geophilidae. 



BIBLIOGRAPHY. The literature of the anatomy 

 and physiology of these animals is very limited. 

 The reader may refer to the following works : 

 Newport, Philosophical Transactions for 1841. 

 Savi, Observazione per servire alia storia di una 

 specie di Julus communissima, Bologna, 1817. Bul- 

 letin des Sciences Naturelles, Dec. 1823. Memorie 

 scientificke di Paolo Savi, Pisa, 1828. De Geer, 

 Abhandlungenzur Geschicteder Insekten, 4to. 1782. 

 Waga, Revue zoologique, par la Societe Cu- 

 vierienne, 1839. T. Rymer Jones, General outline 

 of the animal kingdom. Lond. 1841. 



( T. Rymer Jones.) 



