Mr Daly ell on the Propagation of Scottish Zoophytes, 93 



prominence disappears, the vigour of the hydra is restored, and 

 the tentacula, liberated of the incumbrance effecting temporary 

 obliteration, resume their natural form and functions. Weeks 

 elapse in the course of this process, and during survivance of 

 the animals. Fig. 2, 3. enlarged. 



V. In addition to previous observations the Tubularia indi* 

 visa, I shall merely remark that here and in the Tubularia poly* 

 ceps, a compound uterus of many cysts or sacs is generated on 

 the face of the hydra. Each contains the elements of the pro- 

 geny, expelled in a white, solid, spherical or ovoidal form, whence 

 the external organs are speedily unfolded. But if accidentally 

 retained, evolution succeeds within the cyst, and the tentacula 

 are seen protruding from its orifice previous to expulsion. 

 Probably, therefore, the progeny is expelled as a foetus, invest- 

 ed by an amnios preserving its solid spherical or ellipsoidal 

 form. Borne on the originating tentacula, it enjoys the facul- 

 ty of transition, until reversed and rooted, which succeeds 

 sometimes within two days of expulsion. 



VI. The various species of Scottish Cristatellae propagate 

 under greater analogy to the higher animals, by an ovum with 

 a harder shell and fluid contents. This, after escaping by de- 

 cay of the Cristatella mirabilis, has required 200 or S30 days 

 to mature the young, and 167 days for that of the Cristatella 

 lacustris, when the ovum splits asunder horizontally to allow its 

 exit. 



The adult sertularia and the flustra enlarge by gemmation in 

 its proper sense. Buds are generated at the extremities : each 

 contains a hydra, which bursts the integument investing it, 

 and protrudes from the cell to display its organs. Likewise 

 new cells, formed by the enlarging leaf of the flustra, contain 

 originating hydrse, which, reaching maturity, display their 

 parts. 



But from the preceding observations it appears exceedingly 

 doubtful whether the name of ovum or gemmule can be ap- 

 propriately applied either to the ciliated coi'pusculuvi or 

 plannla as some learned naturalists propose ; perhaps each 

 should be considered rather as an animal advanced a stage 



