On South African Paramphistomidae (Fisch.). 
187 
(Fisch.) (11), and the intermediate host is the small, dark-brown fresh- water 
snail Isidora (Physa) tropica, Krauss. 
Observations on the Early Development of the Eggs of 
P. calicophorum Fisch. 
I collected a number of eggs in a flat dish, filled with water about half 
an inch deep. The eggs are light yellow, elliptical, tapering a little more 
Fig. 9. 
towards the opercular pole than to the opposite pole. Length -17 mm., 
greatest breadth -09 mm. The embryonic cells lie towards the opercular 
pole, and are surrounded on all sides by yolk-cells. The operculum is small. 
Development proceeded under water kept at room temperature (16°-17° C). 
By segmentation the embryonic cells had on the eighth day extended to 
the opposite pole ; the yolk-cells began to break up and diminish in size. 
A membrane of thin flattened cells had grown round the entire cell-mass, 
and one or two large covering cells lay over the anterior extremity of the 
