THE FIGURES. 127 



rounded in a mucoid case. 7 d, a portion of the 

 skin of a fresh-water snail, upon which a number of 

 Cercari(S have become pv/pce ; shghtly magnified. 



7 a and 7 b single pupa highly magnified, and 7 c 

 under the same magnifying power as that under 

 which the Cercaria, fig. 6, is figured. A circlet of 

 spines, which was concealed in the collar of the 

 Cercaria, is at this period very distinct, and pre- 

 sents itself in various positions, according to the 

 motions of the animal within ihQpzrpa case. 



Fig. 8. The animals proceeding from \\\q pupa ; true 

 Distomata; fig. 8 a, an individual extracted from 

 XhQpupa case, and in a rolled up position ; 8 (5, 8 c, 



8 d, individuals which have spontaneously quitted 

 \\iQpupa cases, and have penetrated a short distance 

 into the body of the snail. 8 b still retains the 

 circlet of spines on the collar around the oral orifice. 

 8 c has just lost the spines, the marks of which are 

 still evident on the collar, which is diminishing in 

 size. 8 d an individual more deeply buried than 

 the preceding ones in the body of the snail; the 

 collar still smaller. 8 e and 8/ individuals occurring 

 in the outermost convolutions of the liver. 



