On South African Paramphistomidae (Fisch.). 
189 
aperture is situated a short distance behind the sucker in the adult rediae. 
I counted as many as seventeen daughter-rediae in various stages of develop- 
ment in a parent redia. In many there are less. In some rediae one 
could determine immature from two to three cerceriae with their incipient 
but clearly defined eye-spots and well-defined tails, together with daughter- 
rediae ; and, as one might expect, the immature cerceriae were confined 
to the anterior region and the daughter-rediae to the posterior extremity. 
It seems safe to conclude that the second generation of rediae give rise to 
rediae only, and the third generation give rise to rediae and cerceriae, and 
that the fourth and subsequent generations will behave as the third. 
With regard to the development and generations of rediae and cerceriae, 
Looss (loc. cit., p. 189) states in connection with the life-history of Param- 
phistomum cervi : — 
" Les produits de ces redies commencent a se differ en cier de tres bonne 
heure ; ils prennent naissance et se developpent de la meme maniere 
que les germes des redies de V Amphistomum subclavatum. . . . Mais, 
tandis que chez celui-ci les germes des premieres redies se transforment 
de suite en cercaires, chez YAmphistome conique (x Paramphistomum 
cervi) la seconde generation donne encore des redies. Ces dernieres 
quittent leur mere par un orifice d'accouchement, situe a une courte distance 
en arriere de la ventouse ; elles s'etablissent a cote des redies plus agees, 
s'accroissent et produisent une troisieme generation qui peut etre encore 
une fois des redies. De cette maniere, il resulte finalement un assez grand 
nombre de redies offrant a peu pres le meme aspect et qui commencent des 
lors a produire des cercaires. Chez le ver qui nous occupe je n'ai pas des 
germes de cercaires en compagnie avec des germes de nouvelles redies dans 
une redie mere, comme cela se produit chez le Gastrodisque. Mais cela 
peut etre purement accidentel, car je n'ai pu suivre, aisni je l'ai dit, que 
pendant dense mois le cycle evolutief de ce ver." 
The mature rediae are -6 mm. to 1 mm. in length. The small anterior 
sucker is circular, with a diameter of -05—07 mm. A daughter-redia just 
before birth is -25 mm. long, and the fairly well-developed sucker -05 mm. 
in diameter. The sac-like alimentary canal is well denned. 
The cerceriae are born in a very immature state. They live for some 
time in the liver of the intermediate host, and when mature and capable of 
greater activity they leave the snail. In adult infected snails, as well as 
uninfected specimens, the shells are worn off at the apex, and a part of the 
liver is exposed. It is, therefore, certain that the adult cerceriae emerge 
from the intermediate host through the decaying apex of the shell. They 
may, of course, also leave the snail by the pulmonary aperture. 
As soon as they escape they swim about actively in the water by the 
rapid wriggling movements of the tail. The body is almost entirely opaque 
