296 



ZOOLOGY 



Class II. Onychophora. Peripattis is the best known genus of this class. It 

 is interesting chiefly because it is, in some degree, intermediate between the 

 Annulata and the higher arthropods. They are remarkable for a wide distribu- 

 tion out of proportion to their numbers, and are found in moist places, under 

 wood, stones, and in rotting bark. They agree with the chaetopod annulates 

 (see 276) in the possession of segmental organs (nephridia), a dermo-muscular 

 sac, and poorly developed appendages. The segments are also homonomous 

 (see 264) as in the worms. The relationship to arthropods is indicated by the 

 possession of tracheae, by the substitution of haemocoele (the enlarged lacunae in 



FIG. 135. 



FIG. 135. Caprella geometrlca. From Verrill. X 4. 



Questions on the figure. In comparison with other Crustacea what are the 

 aberrant or peculiar features of this form? See also figures in reference texts 

 (e.g., Parker and HaswelTs Zoology, Vol. I, p. 546). 



which circulation occurs) for the true coelom, and by the differentiation of some of 

 the anterior segmental appendages as mouth parts. The Onychophora resemble 

 the larval condition of those insects which undergo a metamorphosis much more 

 than the adult stages. This suggests that they are more closely related to the 

 ancestral types from which the insects have sprung than to the insects themselves 

 (Fig. 136). 



Class III. Myriapoda (many feet; Centipedes, etc.). Tracheate arthropods 

 with*a worm-like body. Segments numerous, and much alike, one (or, in Dip- 



FIG. 136. 



FIG. 136. Peripatus capensis. From Nicholson after Moseley. 



Questions on the figure. Externally in what respects is this form like the An- 

 nelids ? In what respects different from them ? Of what special zoological interest 

 is this genus? What are its habits? In what respects is it like and in what unlike 

 the centipede (Fig. 137)? 



lopoda, two) pair of appendages to each segment. The head is distinct and bears 

 antennae and mouth parts. The eyes are numerous and simple (ocelli). In 

 fundamental structure and development the myriapods resemble insects. There 

 are two principal orders. One embraces the centipedes which are carnivorous, 

 have biting jaws, have one pair of appendages to each segment, and are poisonous. 

 The second includes the millipedes which are vegetable feeders and possess man- 



