THE WHIP WORM. 213 



3. Accurate measurements. 



4. Shape and description of head and tail ends. 



5. Character of movement. 



Key to Filarial Larvae. 



A. Sheath present. 



1. No periodicity. 



F. philippinensis. Tightly-fitting sheath; not flattened out beyond extremi- 

 ties. Tail is pointed and abruptly attenuated. Lashing progression move- 

 ment. 320x6.5/4. 



2. Periodicity exhibited. 



a. Nocturnal periodicity. 



F. bancrofti (F. nocturna). Pointed tail; loose sheath; lashing movement. 

 300x7.5/4. 



b. Diurnal periodicity. 



F. loa (F. diurna). Pointed tail; loose sheath; cannot be distinguished 

 from F. nocturna except by periodicity. 300x7. 5/4. 



B. Abscence of sheath. None of these exhibit a periodicity, being continuously 



present. 



1. Blunt tail F. perstans. 200x4.5/4. 



2. Sharply-pointed tail: 



a. F. demarquayi. 210x5/4. 



b. F. ozzardi. 215x5/4. 



NOTE. A filarial embryo, F. powelli, reported once. It has a sheath, nocturnal 

 periodicity, and is about 130x5/4. 



TRICHOTRACHELID^:. 



These have a long thin neck and a thicker terminal portion. The 

 oesophagus is of the single row of cells type. The anus is terminal; 

 there is only one ovary. 



Trichocephalus trichiurus. This is usually called the whip- 

 worm the thickened body representing the handle and the narrow 

 neck the lash. It is one of the most common parasites in both temper- 

 ate and tropical climates. The egg is very characteristic in having an 

 oval shape with knobs at either extremity. It resembles a platter with 

 handles. The male is almost 2 inches long, and has the terminal 

 portion curled up in a spiral. It has a single terminal spicule. 



The female is a Jittle longer than the male, and has the terminal 

 part in the shape of a comma instead of being coiled. The neck only 

 contains the cesophagus. The great powers of resistance of the ova 

 may account for their general distribution; they may live for months 

 under conditions of freezing and so forth. There is no intermediate 



