MYRIAPODA : PROTRACHEATA. 519 



Regeneration of lost parts, Newport, Ph. Tr. 134, 1884. 



Scolopendrella ( = Symphyla) is placed by Packard with the Thysanura among 

 Insecta. Its mouth-parts are sunk into the head as in Collembola and Campodea \ 

 but there are many discrepancies in the accounts of its anatomy, and at present it 

 is perhaps better to leave its position undefined. There is of course nothing in- 

 trinsically improbable in the existence of an Insect with very similar somites and 

 fully developed jointed abdominal limbs. Packard, American Naturalist, xv. 1881; 

 Wood Mason, A. N. H. (5), xii. 1883; Ryder, Proc. Amer. Nat. Soc. Philadelphia, 

 1881; Grassi, Atti R. Accad. Sc. Torino, xxi. 1885 ; Latzel, op. cit. supra. 



CLASS PROTRACHEATA. 

 (Onychophora, Peripatidea.) 



Tracheate Arthropoda with soft, worm-like bodies, a pair of antennae, 

 and a series of paired imperfectly jointed limbs. Tracheal stigmata mimeroiis 

 and scattered ; nephridia or segmental organs present. A single genus 

 Peripatus. 



The body is not segmented, and is flat ventrally, convex dorsally. 

 The ringed antennae are large. There is a buccal cavity inclosed by soft 

 lips and containing the first pair of limbs, which are 2-clawed and act 

 as jaws. The second pair of limbs form the oral papillae placed at the side 

 of the mouth, at the summits of which open the receptacles of the slime 

 glands. The remaining limbs are placed at equal distances as far as the 

 posterior extremity of the body. The number of pairs varies in the different 

 species (from 14-30) *. In P. capensis the limb is originally 5-jointed, but 

 in the adult the jointing becomes obscure. In all the species it is ter- 

 minated by two chitinoid claws. A pair of anal papillae by the side of 

 the genital aperture appears to represent the last pair of limbs, as in some 

 specimens of P. capensis they possess the two typical claws. 



In P. capensis there is a delicate cuticle, a single layer of ectoderm (hypo- 

 dermis) cells ; an outer layer of circular muscles ; an inner layer of longi- 

 tudinal muscles arranged in five bands, two dorsal, two lateral, and three 

 ventral ; and a layer of transverse, i. e. dorsoventral muscles placed obliquely 

 and dividing the coelome into three longitudinal cavities, a median con- 

 taining the digestive tract, slime glands, and genitalia, and two lateral con- 

 taining the salivary glands, nerve cords, and in the male the last enlarged 

 pair of crural glands. The limbs contain a separate division of the coelome 

 which lodges the crural glands and nephridia. The middle compartment 



1 Ernst states (Nature, xxiii. p. 447) that a young Peripatus (? P. Edwards?) possessed at birth 

 29 pairs of feet, the adult 31 ; consequently new pairs of feet must be added during growth. He 

 also observed a skin cast by the young, animal. The fact that there are jaws and claws in reserve 

 points to the probability of a moult occurring from time to time. For observed variations in the 

 number of feet, cf. Moseley, 'On the Species of Peripatus' A. N. H. (5), iii. 1879, p. 263. 



