52 



COE 



and somewhat nearer the median line is a pair of clusters, each of 

 which likewise contains 8 to 12 ocelli. These posterior groups lie 

 immediately above the brain. Smaller and evi- 

 dently younger individuals have but 4 to 6 eyes in 

 each of the four groups. There is considerable 

 variation in the size of the ocelli. 



Proboscis. — The proboscis sheath reaches nearly 

 to the posterior end of the body. The proboscis is 

 rather slender but may be contracted so that its di- 

 ameter is equal to more than half that of the body 

 itself. The proboscis is commonly attached to the 

 proboscis sheath at a point situated from ys to }( 

 the distance towards the posterior end of the body. 

 The armature is weaker than in A. exilis. The 

 central stylet is moderately slender and acutely 

 pointed. Its basis is somewhat conical in shape, 

 contracted slightly toward its middle portion (p1. 

 VII, fig. 6), and is rounded at its larger, posterior 

 It is slightly longer than the stylet itself. The number of 



Fig. 13. Amphi- 

 poms leuciodus. 

 Outline of anterior 

 portion of the body 

 showing brain and 

 arrangement of the 

 ocelli. X 12. 



end. 



pouches of accessory stylets is commonly three, although there are 

 sometimes only two, and occasionally a specimen is found which has 

 four. There are usually two or three stylets in each pouch. In a few 

 instances, however, four and five were observed. Where three pouches 

 are present, as is usual, they are situated at nearly equal distances on 

 the circumference of the proboscis (p1. vii, fig. 6). 



Cerebral sense orga7is. — Moderately small and situated well in front 

 of brain and on ventral side of head. They communicate with the 

 exterior by means of a pair of canals which open on the latero-ven- 

 tral margins of the tip of the head. 



Nephridia. — The nephridia reach forward to the brain region. 

 There are several pairs of efferent ducts, some of which ojDen on the 

 ventral, and some on the dorsal surface of the body. In one of the 

 specimens sectioned the first pair of efferent ducts extended from the 

 internal side of the lateral nerve cords and opened directly to the 

 latero-ventral aspect of the body after passing on the ventral side of 

 the nerve cords. A little farther back in the esophagal region were 

 two efferent ducts on one side and one on the other which passed above, 

 and externally to the nerve cords to open likewise below the lateral 

 margins. In the remainder of the esophagal region were three more 

 efferent ducts on each side. With one exception all of these passed 

 above the lateral nerves and opened on the dorso-lateral surfaces of the 



