110 ZOOLOGY. 
found in man, the former in a Lascar, the latter in an 
Egyptian boy. 
Bilharzia hematobia 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 eanal or passage in the male formed by the infolding of 
the edges of the concave side of the body, called a gynceco- 
phore. 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 Rudolphi (Fig. 
72), 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, Polystomee, 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. 72 —1. Le hloridium par ; : . i 
living’in the tentacles of Suceinea ; 2Aful. cola Baer, which inhabits 
grown nurse-Leucochloridium with the nurse- : : : 
stock from which it has grown. Natural size. the pericardi al cavity of 
—After Zeller, 
aan 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~ 
