3254 



THE JOINTED ANIMALS 



SCALE-TAILED APUS, Lepidurus 



(Natural size.) 



Class Prototracheata 



This term is applied to the group now claiming attention, because in many 

 respects it occupies a place between the Tracheates and Worms, and is consequently 



regarded as allied to the ancestral form from which all 

 Tracheates have been evolved. Unlike the true Arthro- 

 pods, the limbs are not jointed; and the tough integument 

 is covered with bristle-bearing papillae, but is not divis- 

 ible into segments. The long body is shaped like that 

 of a caterpillar or slug, and to the sides of its lower sur- 

 face are attached a number of short more or less conical 

 legs; each tipped with a pair of strong claws. The head 

 is supplied with a pair of stout longish antennae, at the 

 base of each of which, on the outer side, is an eye. On 

 the lower surface of the head is placed the mouth, sup- 

 plied with fleshy lips and two pairs of toothed horny 

 jaws; and on each side of the head there is a modified 

 appendage known as the oral papilla. The chief features 

 to note in the internal organization are the presence of 

 segmentally arranged kidneys one opening at the base 

 of each leg and the wide separation of the two strands 

 of the ventral nerve chord. This last characteristic is 

 found in some of the lower worms, and the numbers of 

 paired kidneys in the higher members of the latter group. 

 The class contains only the single family Peripatidce ', 

 which has a wide but somewhat singular distribution. 

 The genus Peripatus, for example, is spread over the 



, . . , . ,. x . , 



West Indian islands, ranging from Nicaragua through 

 th e northern parts of South America to Chili, and has 



MALE OF BRINE SHRIMP, 



temia saiina (enlarged). also a single representative in Sumatra; while Pen- 



MALE OF Branchipus grubet 



(natural size) ; *. FEMALE OF 



