XII] 



PROTOTRACHEATA 



227 



embryology. One species lays 

 eggs and the others produce 

 living young. 



That the animal is a most 

 interesting "missing link" be- 

 comes evident if we attempt 

 to sum up the Annelidan and 

 the Arthropodan features of 

 its anatomy. Thus Peripatus 

 resembles Annelida in the 

 nervous system, the muscular 

 pharynx, the structure of the 

 eyes, the serially repeated 

 "nephridia," the shortness of 

 the stomodaeum and of the 

 proctodaeum, the thinness of 

 the cuticle and the hollow 

 nature of the paired ap- 

 pendages; but in the reduction 

 in size of the coelomic spaces, 

 the presence of a wide haemo- 

 coele and of tracheae, the 

 nature of the antennae and of 

 the heart and pericardium, the 

 position of the genital pore and 

 the presence of true gnathites, 

 Peripatus approaches the 

 Myriapods and Insects. 



In habits these animals are 

 shy and inconspicuous, hiding 

 under bark or stones and pre- 

 ferring moist surroundings. 

 They avoid the light and 

 move with deliberation, test- 

 ing the ground as they advance 

 with their antennae. 



FIG. 93. Peripatus capensis, male, dis- 

 sected to show the internal organs x 2. 

 After Balfour. 



1. Antennae, showing anteunary nerve. 

 2. Oral papilla. 3, 3', 3 10 . 1st, 2nd 

 and 10th leg of right side. 4. Brain 

 and eyes. 5. Circum-oesophageal 

 cord. 6. Ventral nerve-cord of right 

 side, showing the transverse commis- 

 sures. 7. Pharynx. 8. Stomach. 

 9. Anus. 10. Male generative open- 

 ing. 11. Salivary glands. 12. Slime 

 glands and reservoir. 13. Enlarged 

 crural gland of the 17th leg. 14 4 , 

 14 10 . 4th and 10th nephridia of right 

 side. 



152 



