Mr. Newport on the Class Myrlapoda, Order Chilopoda. 4*27 



Family 5. Geophilid^, Leach. 



The Geophilidce connect the Arachnidan type of Myrlapoda with the Anne- 

 lida, as the lulldce also connect the Crustacean type with the same class. 



The Geophilidce (Tab. XXXIII. figs. 10 to 19; and Tab. XL. figs. 12, 13.) 

 have the body slender, greatly elongated, and formed of a multitude of seg- 

 ments, each of which bears a single pair of spiracles and legs. The number 

 of moveable segments in this family varies from about thirty-five to more than 

 two hundred. It is not characteristic of genera, as in the other families of 

 Chilopoda, but it seems, within slight limits, to mark each particular species ; 

 although even in the individuals of each species there is a little variation. 

 This is an exceedingly important fact, since, although the exact number of 

 segments is not always the same in each individual, it rarely or ever exceeds 

 certain extremes ; and thus, while we are enabled to employ the average num- 

 ber as a character for species, we are led to important considerations with 

 reference to the comparative physiology and development of the species, as 

 well as of the two sexes, in the whole of the Articulata. Thus I have inva- 

 riably found that the male Geophili have fewer segments than the female. 

 The males oi Artlironomalus longicornis have fifty-one or fifty-two leg-bearing 

 segments, while the females usually have fifty-three or fifty-four. The full- 

 grown females of Geophilus terrestris have eighty-three or eighty-four pairs of 

 legs and segments, but the very young have only seventy-nine, and the males 

 of the same species eighty-one or eighty-two. The extreme variation in these 

 species is thus four or five segments and pairs of legs. In a large Neapolitan 

 species, Geophilus laevigatus, Bruhl. ? the variation is somewhat greater. Thus 

 in eight males the number varied between ninety-six and ninety-nine, while 

 in eleven females it ranged between one hundred and three and one hundred 

 and seven ; and of two female specimens of Geophilus sulcatus, one individual 

 had one hundred and thirty-six segments and pairs of legs, and the other one 

 hundred and forty. Each of these moveable segments in the adult Geophilus 

 is formed of two unequal rings, the posterior of which is much the largest, and 

 alone bears the spiracles and legs. These rings, even in an advanced stage of 

 the embryo, before quitting the egg, and before any appendages are developed, 

 are themselves distinct segments of equal size, which become anchylosed to- 



