DR. THEODOR NEUMANN. 237 



course. Several kinds of this way of reproduction are 

 possible. It may happen through division, the whole 

 body falling into two or more parts, which then form 

 separate organisms, or by budding, when the individual 

 pushes out small protuberances, "buds," which later 

 drop off and form animals themselves. 



A third kind of reproduction is possible and especially 

 found in some of our most interesting and also most 

 dangerous parasites, that of sporocysts, — internal bud- 

 ding. These forms are pioduced inside the body of the 

 individual parasite ; they are egg-like cells, separated 

 from the inner walls of the body, falling into its cavity 

 and then growing up. Before they get outside they 

 must break through the walls of their birth-place, either 

 by means of a previous hole or by tearing the enclosure. 

 This kind of development mainly happens among the 

 trematods or flukes. The simplest imaginable case would 

 be when the progeny produced by the sexual animals 

 in sexual way, after passing through a stage of free 

 life, get into an intermediate host, but do not encyst 

 here nor wait for a re-transportation into the linal host, 

 but develop into creatures different from the parents, 

 which creatures produce now in a sexual way a new gen- 

 eration. The latter take early the shape and form of 

 their grandparents and are, after having finished their 

 development, transported passively into their original 

 host, where they become sexual individuals. In opposi- 

 tion to the latter the other, a sexual generation, has been 

 called ''nurse." 



Some species of Distomum present a still more compli- 

 cated form of development : the embryos develop into a 

 " sporocyst " or a " redia," both of which may by means 

 of internal budding produce a generation of so-called 

 "cercaria," which become free, then encyst in the body 

 of a second intermediate host after losing the sting 

 near the mouth and tail, and being finally transported 



175 



