. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. OVUM. 23 Fig. 19. on leaving the parent body they become deve- their early state present some very striking loped into a ciliated embryo, which, for a time, phenomena of metamorphosis, yet there is moves freely about, then becomes fixed, un. nothing in either which fully deserves the name dergoes farther changes in being developed, of alternate generation, for all the individuals of which these compound animal structures consist are alike sexually perfect, and there does not appear to subsist any necessary con- nection b
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. OVUM. 23 Fig. 19. on leaving the parent body they become deve- their early state present some very striking loped into a ciliated embryo, which, for a time, phenomena of metamorphosis, yet there is moves freely about, then becomes fixed, un. nothing in either which fully deserves the name dergoes farther changes in being developed, of alternate generation, for all the individuals of which these compound animal structures consist are alike sexually perfect, and there does not appear to subsist any necessary con- nection between the nonsexual process of multiplication, and the subsequent exercise of the sexual function. There are,in fact, scarcely any intermediate stages of non-sexual exist- ence such as are described in the true in- stances of alternate generation. It is deserving of notice, however, that Lowig and Kiilliker are of opinion that in some of the Botryllidie numerous embryoes are at once developed from a single ovum by its division, these indi- viduals subsequently multiplying by gemma-. tion into the perfect sexual animals. A series illustrating the development bi/ ova of Pedi- cellaria. {After Van Beneden.') and now from its own body in some, and in others only from the spreading part of the stem or base which supports it, proceeds the gemmation of other individuals of the colony, all of which apparently are capable of sexual generation when they arrive at The Ascidian Tunicata present another mo- dification of the reproductive process now under consideration. Two forms of these animals exist, both perfect, viz. the simple and the compound; but these are not related to each other in the same manner as the two kinds of Salpians; for each kind is capable of propagating its like by generation. The soli- tary ones rarely multiply by gemmation, and when they do so the individuals separate from the stock; but the compound animals always undergo this mode of multiplication,
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