DICROCCELIUM LANCEATUM STILES AND HASSALL 69 



of a number of unicellular glands surrounding the uterus imme- 

 diately behind the opening of the common yolk duct. Each 

 gland opens into the uterus by means of a separate duct. 



Apparently both cross and self-fertilization are possible. In 

 both cases the organ of copulation is the cirrus, but in the case of 

 self-fertilization it is introduced into the female genital opening 

 of the same individual. The sperm travels all the length of the 

 uterus till it reaches the duct of the receptacle and finally 

 the receptacle itself. The eggs produced in the ovary slip 

 down the oviduct and become fertilized by the sperm stored 

 in the receptacle as they pass by the opening of its duct. Yolk 

 from the yolk glands is added to each fertilized egg as it passes 

 by the opening of the common yolk duct. Finally a shell is 

 formed around each egg from material furnished by the yolk l 

 gland and the now completely formed egg travels down the 

 uterus followed by other eggs, until the uterus is completely 

 filled. A well developed uterus may harbor over a million eggs. 



Development. The eggs develop in the uterus but the 

 little embryo remains inclosed in the eggshell and does not leave 

 it until the egg has been swallowed by a snail. The eggshell 

 loses its little lid under the influence of the digestive juices and 

 sets free the larva which is called miracidium and is provided 

 with a ciliated ectoderm. This larva finally manages to get into 

 the liver of the snail, but in doing so it strips itself of its ciliated 

 ectoderm. The further development of D. lanceatum has never 

 been observed, but we must assume that it is essentially the 

 same as in its better known near relative, the large liver fluke 

 Fasciola hepatica. Here the larva grows into the new stage 

 known as sporocyst. The sporocyst soon produces by a special 

 kind of internal budding a number of redice or larvae of the 

 second generation. Each redia produces by a similar process a 



1 The gland formerly known under the name of "shell-gland" and 

 described here as Mehlis' gland does not produce the shell, but probably 

 secretes a liquid in which the eggs are suspended. See Goldschmidt, Zool. 

 Anz. 1909. 



