110 ZOOLOGY. 



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

 Egyptian boy. 



Bilharzia hcematobia 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 //. venarum Treutler, the latter occurring in 

 the veins (Cobbold). 



The nurse of Distomum macrostomum Rudolphi (Fig. 

 72), described under the name of Leucoeliloridiiim, is 

 cylindrical, and strongly resembles a maggot ; its strange 

 habitat is the tentacles of a snail (Succinea). 



Of the second suborder, Polystomece, 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 conclii- 



Fip. 72 1. Lntcochlnridi'im paradoxum, 7 T> i i i i -.L 



living In the tentacles of Succinea; 2 A full- COM i>aer, WhlCll inhabits 



grown nurse-Leucochloridiinn with the nurse- ,1 j- ^ . 



stock from which it has sroun. Natural size. the pei'lCai'dUll Cavity OI 



After Zeller. T , , 



fresh-water mussels, and 



also is an ectoparasite of fresh-water fishes. Diplczoon 

 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 ofDiporpa. 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- 



