178 INVEBTEBBATE MORPHOLOGY. 



tive tissue beneath the skin, producing ulcers, at the bottom of which the 

 worm lies coiled up. The ova develop in water and the embryos pass 

 probably into small Crustacea, which are swallowed with drinking-water. 

 Filaria sanguinis hoininis, also solely trppical in its distribution, 

 receives its name from the fact that it lays its ova in the blood of man, 

 which may thus swarm with countless numbers of small worms. These 

 make their way to the exterior of the body by the kidneys, producing 

 haemorrhages or minute abscesses in that organ and, as the result of 

 these, milky or bloody urine. 



2. Order Gordiacea. 



This order includes the families of the Gordiidce and Mer- 

 mithidoe, long slender thread-like worms, which differ from the 

 Eunematoda in several important respects. They occur in 

 their mature state in fresh water ; in their immature stages, 

 howeyer, they are parasitic in insects. In the adult Gordius 

 the mouth is usually closed by an overgrowth of the cuticle, 

 and the anus is lacking in Mermis. The musculature of the 

 body-wall consists only of longitudinal fibres (Fig. 89, m), which 



d 



Fig. 89. — Teansvehsb Section op Oordius (after Vejdovskt). 

 cu = cuticle. n = nerve-cord. 



d = Intestine. pe = peritoneum. 



hy = hypodermis. 'ut = uterus. 



m = lougitudinal muscles. ov = oviduct. 



differ in their arrangement from those of the Eunematoda in 

 being interrupted only in the mid-ventral line. The coelom 

 is lined by a peritoneal epithelium (pe) lying beneath the 



