Transmission 



37 



needle and to cut outwards with the second. In our experience 

 the spear-shaped steel points issued for use on gramophone records 

 when fixed in needle-holders are far more satisfactory than ordinar}' 

 dissecting needles for this work. With them a large window can 

 be quickly cut in the hardest shells and the molluscan body rapidly 

 dragged out complete. The liver, which occupies the upper or 

 central whorls of the gastropod shell, is the usual site of election 

 for the developmental stages of trematodes. But a detailed 

 examination of the mollusc is practically never necessary for the 

 determination of an infection. With the first tear, as a rule, the 

 characteristic bodies flood out in numbers into the surrounding 

 plasma and water, while further search may be made under a low 

 power by squashing the whole molluscan body slightly between 

 two slides. In this way over 3,300 samples were minutely examined 

 in the course of the inquiry. As shown in the appended list, 

 seventeen species of Trematode larvae were identified during these 

 dissections. A number of new species were found also. 



List of Trematode Larv.e identified in Egyptian IMolluscs. 



^lelania 



Vivipara 

 Lanistes 



(13) Cercaria plcurolopliocerca -r 



(14) Cercaria celhdosa — 



(15) Cercaria monostomiverrucostan — 



(16) Cercaria microcristata + 



(17) Cercaria microcotyla + 



(18) Cercaria piisilla — 



(19) Cercaria sp. ? - 



Recognition op Bilharzia Cercaria. 



The adult bilharzia worm resembles the other distome trema- 

 todes in possessing well-developed oral and ventral suckers, but differs 

 in two remarkable ways : the sexes are separate, and there is an 

 absence of a definite muscular pharyngeal bulb at the commencement 

 of the oesophagus (fig. 21). As in all parasitic worms the infective 



