152 ZOOLOGY. 



found in man, the former in a Lascar, the latter in an 

 Egyptian boy. 



Billiarzia hmmatoUa Cobbold is common in the portal 

 system of blood-vessels and in the veins of the mesentery, 

 bladder, etc., of Egyptians, and has caused an endemic dis- 

 ease at the Cape of Good Hope. In Egypt, out of three 

 hundred and sixty-three post-mortem examinations, this 

 worm occurred one hundred and seventeen times. It is 

 bisexual, the female greatly smaller than the male, living in 

 a canal or passage in the male formed by the infolding of 

 the edges of the concave side of the body, called a gynceco- 

 pliore. There are three other rare human flukes known : 

 Tetrastoma renale Delle Chiaje, Hexathyridium pinguicola 

 Treutler, and H. venarum Treutler, the latter occurring in 

 the veins (Cobbold). 



The nurse of Distomum macrostomum Rudolph! (Fig. 

 102), described under the name of Leucochloridium, is 

 cylindrical, and strongly resembles a maggot ; its strange 

 habitat is the tentacles of a snail (Succinea). 



Of the second suborder, Polystomem, the species have two 

 small anterior and one or several posterior suckers, and a 



pair of eyes. They are 

 mostly external parasites, 

 like the leeches, and un- 

 dergo no metamorphosis. 

 In some forms the body 

 is segmented. 



A type of this suborder 

 is Aspidogaster conchi- 



Fig. 102. 1. Lnicochlwidium paradoxum. 7-0 i i i i -j. 



living in the tentacles of Succinea; 2. Afull- COM mer, WlllCll inhabits 



errown nurse-Leucochloridium with the nurse- ,> j i j. a 



stock from which it has grown. Natural size. tllC periCardial Cavity 01 



fresh-water mussels, and 



also is an ectoparasite of fresh-water fishes. Diplozoon 

 consists of two Trematodes very intimately united into an 

 X -formed double animal. In the young stages the two ani- 

 mals are separate, and in this state were described under the 

 name of Diporpa. Diplozoon paradoxum Nordmann lives on 

 the gills of numerous fresh-water fishes. Polystomum has 

 a flat body, without suckers on the fore end, with six suck- 



