METAZOA MALACOPODA. 381 



places, preeminently under the bark of decaying stumps, 

 the legs are soft and fleshy ; hence the name of Mal- 

 acopoda. The leg proper is provided with many rings of 

 papillae and at its lower end are three pads. The foot 

 carries two claws and several papillae (PI. 940, fig. 3). 

 At the bases of the feet on the ventral surface the paired 

 excretory organs or nephridia open. The presence of 

 these organs in Peripatus recalls the similar organs we 

 have already found in Worms. 



Peripatus breathes by means of tracheae which, how- 

 ever, do not appear until the animal is hatched. 1 The 

 spiracles are scattered irregularly over the body, each 

 spiracle (PI. 940, fig. 4) leading into a tracheal pit 

 which spreads out into a bundle of tracheal branches 

 (see fig. 4) that never unite. 



Peripatus is viviparous, the period of gestation cover- 

 ing thirteen months ; this being the case, a comparatively 

 small number of individuals is produced and these re- 

 semble the parent at birth excepting in color. While the 

 adults of P. capensis are of a rich green, the little ones 

 ar'e nearly white with green antennae. According to 

 Steel, the animals cast their skins like many insect 

 larvae, and the cast skins are generally worked over with 

 the jaws and finally swallowed. 



The general more or less slug-like appearance and the 

 possession of a nervous system similar to that of Chiton 

 caused some naturalists to place Peripatus among the 

 Mollusca. Its closer resemblance in form to the Worms, 

 the possession of paired appendages along the whole 

 length of the body, and still more the presence of rows 

 of paired nephridia caused naturalists later to place 

 Peripatus in the subkingdom of Vermes. 



The discovery of true tracheae and spiracles, the pos- 

 session of jointed antennae and legs, the existence of 

 appendages modified as jaws, and of certain important 



1 Packard, Text-book of Ent., 1898, p. 15. 



