CHAPTER XI. 



THE PEEIPATIDEA, THE MYZOSTOMATA, THE EXTEROPNEUSTA, 

 THE CH^TOGXATHA, THE NEMATOIDEA, THE PHYSEMARIA, 

 THE ACANTHOCEPHALA, AND THE DICYEMIDA. 



I HAVE reserved for discussion in this chapter the Peripa- 

 tidea, which have heretofore been referred by most authors to 

 the Annelida ; and certain groups of the lower Metazoa^ the 

 precise morphological relations of which are as yet uncertain, 

 although it is pretty clear that several of them are allied with 

 the lower Annelida, the Rotifera, and the Tarbellaria. They 

 are, for the most part, totally devoid of segmentation ; while 

 the Chcetognatha and the Myzostomata alone present any 

 structures resembling limbs, though the nature of these is 

 doubtful. So far as the nervous system is clearly made out, 

 it exhibits no such chain of post-oral ganglia as characterizes 

 the higher worms. 



The Peripatidea. — At p. 225, I have referred this group 

 to the Arthropoda, Mr. Moseley's memoir on Peripatus ^ hav- 

 ing left no doubt upon my mind, that he had satisfactorily 

 proved the justice of the surmise respecting its affinities 

 originally made by Gervais. It is only recently, however, 

 that I have been ai3le, thanks to Mr. Moseley, to examine one 

 or two specimens of Peripatus JSFovm Zelajiioe, and to satisfy 

 myself of the main point, namely, the existence of the tra- 

 cheal system which he has described. 



Of the Q-enus Peripatus several species are now known, 

 from the West Indies, South America, the Cape of Good 

 Hope, and New Zealand, where they are found among the de- 

 caying wood of damp and warm localities. They have the 



1 " Philosophical Transactions," 1874. See, also, the valuable memoir of 

 Grube, " Ueber den Bau von Peripatus Edwardsii " (" Archiv fur Anatomie," 

 1853). 



