174 RESEARCHES IN HELMINTHOLOGY AND PARASITOLOGY. 



succeeding segments. The podal hooks, Fig. 5, of the anterior 

 segments are about 0.05 to 0.06 mm. long, and con.sist of a long, 

 curved handle, ending in a small recurved hook. 



The podal hooks of the posterior three setigerous segments form 

 close transverse rows, Fig. 6, of variable number, from 9 to 24 in 

 each row. The hooks are minute, and measure from 0.025 to 0.03 

 mm. long. They consist of a broad handle, ending in a lateral 

 comb-like extremity, as represented in figure 7. 



The number of podal setae and podal hooks is more or less vari- 

 able in the corresponding segments of different individuals, and 

 frequently, also, on the two sides of the segments of the same in- 

 dividual. The difference is due sometimes to the accidental loss of 

 some of the appendages ; sometimes, probably, to circumstances 

 interfering with their development. In several specimens the fol- 

 lowing differences were observed : 



Specimkn I. 



First segment, 6 and 8 setae. 



Second to fourth segment, inclusive, 8 to ro setse and 4 to 5 

 hooks. 



Fifth to eighth segment, inclusive, 6 to 8 setae and 4 to 5 hooks. 



Ninth segment, 6 setae and 9 to 22 hooks. 



Tenth segment, 4 setae and 12 and 18 hooks. 



Eleventh segment, 3 and 4 setae and 12 hooks on each .side. 



Specimkn 2. 



First segment, 8 setae on each side. 



Second to sixth segments, inclusive, 8 setae and 4 hooks on each 

 side. 



Seventh and eighth segments, 6 or 7 setae and 4 hooks, except on 

 one side of the eighth segment, in which another fascicle of 6 setae 

 substituted the usual fascicle of hooks. 



Ninth segment, 6 setae on each side and 9 and 20 hooks. 



Tenth segment, 4 and 5 setae and 13 and 16 hooks. 



Eleventh segment, 3 and 4 .setae and 12 hooks on each side. 



Specimen 3. 



First segment, 8 setae each side. 



Seven succeeding segments. 6 to 10 setae and 3 to 4 hooks each 

 side. 



Ninth segment, 7 setae and 24 hooks each side. 



