. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 30 OVUM. not itself converted by any direct process of development or metamorphosis into a perfect Distoma, but lias gradually formed from germ- cells within it a progeny, sometimes of one, more frequently a number of bodies, which, when they arrive at maturity, present each one an external form and internal structure and locomotive powers, entitling them to be con- sidered as independent animals. Nor are these directly converted into Distomata ; but again there is formed within the body of each, and in the same gradual
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 30 OVUM. not itself converted by any direct process of development or metamorphosis into a perfect Distoma, but lias gradually formed from germ- cells within it a progeny, sometimes of one, more frequently a number of bodies, which, when they arrive at maturity, present each one an external form and internal structure and locomotive powers, entitling them to be con- sidered as independent animals. Nor are these directly converted into Distomata ; but again there is formed within the body of each, and in the same gradual manner from germ-cells, a new progeny of animals nearly similar to those producing them and equally differing from the complete Distomata. Each of this new progeny, as it increases in size, has formed within it by development from germ-cells the third progeny of the series, and the last of the cycle ; but these are different from their immediate parents, and in their internal or- ganisation scon manifest the type of the true Trematode. These animals are endowed for a time with very active locomotive powers, to which a long caudal appendage con- tributes ; their two progenitors have been confined in the parasitic condition, but these Fig. Series of changes in the development and generations oj Distoma. (From Steejistrnp.~) o, Ovum with embryo or larva developed in it. e, this embryo in a free moving state; e', another embryo in its interior. (These are of Monostomum mutabile, from V. Siebold.) E, this last embryo farther advanced. 1, first stage, soon after it becomes free; 2 and 3, farther on, with g, the second generation, within them in various stages. o, 1, one of this second generation at an early period of its advancement; 2 and 3, farther on, with c, c, Cercariae or Distoma-larvse, within them; g', one of the granular globules from which the Distoma larv» and previous generations arise near the posterior part of the body. c, one of the Cercarise or Distoma larva wi
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