290 Mr. Newport on the Class Myriapoda, Order Chilopoda, 



distinct in Geophilus, the sub-basilar segment (c), that gives origin to a dimi- 

 nutive pail* of appendages, — the first pair of legs (figs. 16 and 19.). In Scolo- 

 pendra the whole of these parts form one structure (fig. 4. b, c). The second 

 of the original basilar segments has not only encroached on the first, which is 

 reduced to a narrow lunated fold on the upper surface, but the third segment 

 has entirely disappeared, and the fourth, or sub-basilar of Geophilus, is also 

 united with it on its upper surface, but retains its original distinction, with 

 its diminutive first pair of legs on the under surface (fig. 5.). 



These are the parts that constitute the head and organs of nutrition in 

 Myriapoda, analogous to those which form the head of true Insects. 



It has been objected by some naturalists that the foot-jaws of Myriapoda do 

 not properly constitute part of the organs of nutrition ; but on tracing the 

 development of the parts, as just described, their perfect identity with the 

 mandibles of Insects is clearly indicated. The basilar region, which in Geo- 

 philus and Scolopendra is of great extent, is very much reduced, and the 

 cephalic enlarged, in Lithohius (fig. 29.) ; and this change is carried still 

 further in Cermatia (fig. 36.). In Lithobius the distinction between the ante- 

 rior and the two posterior subsegments is marked by a deeply-impressed, 

 lunated sulcus, and the posterior part of the cephalic region of the head is 

 greatly enlarged (a), while the basilar region is reduced to a narrow trans- 

 verse ring (b, c), and the minute first pair of legs attached to this region in 

 Scolopendra have entirely disappeared. This change is carried still further in 

 Cermatia, in which the cephalic region (a) of the head is enormously deve- 

 loped, as also are the organs of sense, and the whole approaches nearer to 

 that of Insects. The basilar region also has united with the cephalic, leaving 

 only its narrow ventral plates, as we shall hereafter find in lulus, while the 

 mandibles also [g, h, i, m) are enormously developed. 



Thus, then, by tracing the changes of the Myriapod from the ovum, and 

 comparing the adult forms of different genera, we are enabled to ascertain the 

 number of the rings that enter into the composition of the head, and also to 

 confirm the original views of Savigny, that the parts of the mouth are the 

 analogues of the organs of locomotion, and acquire their various forms in 

 consequence of the different extent to which their individual parts are deve- 

 loped. 



