152 Dr Grant on the spmitaneous Motions of 



rents along the surface of the contained ova, and that particu- 

 lar vibrating zone immediately around them, which we always 

 observe along a ciliated surface, when the ciliae are in too rapid 

 motion to be distinctly seen. On allowing the three ova to es- 

 cape into the water of the watch-glass, by tearing open the cap- 

 sule with two needles, they immediately began to glide to and 

 fro along the bottom, and I could now perceive the cilia? vibrat- 

 ing on their surface as they moved forward. The ova of this 

 minute zoophyte are very numerous, amounting to twenty or 

 thirty in each vesicle, which is probably the reason of the poly- 

 pi-like capsules, to allow so many ova sufficient space to deve- 

 lope themselves on the outside of the vesicles. I have never ob- 

 served more than two ova in a vesicle of the PlumulariaJMcatay 

 and they have space to arrive at full maturity within that vesi- 

 cle. The ova of the Camp. di(;hoto7na are very minute, regularly 

 formed oval bodies of a semiopaque milk-white colour ; the ciliae 

 distributed over their surface, propel them only in one direction ; 

 their motions and general appearance, like those of other ova, 

 are so peculiar, that they are easily distinguished from animal- 

 cules, by any person who has once examined the mature vesicles 

 of a zoophyte. The cilia on the surface of these and other ova 

 are minute filaments, which may be compared to the small hairs 

 covering the human body ; they do not add to the internal or- 

 ganization of the ovum, nor render it as complex as that of the 

 adult animal which possesses highly organized polypi ; they are 

 organs which exist in the adult zoophyte, and in the simplest 

 known forms of animal matter, the motions of the simplest gela- 

 tinous animalcules being performed by them ; and they are ne- 

 cessary to prevent the ova from falling by their own gravity like 

 the seeds of plants, to be buried in the ever-moving sands. 



Cavolini prosecuted for two successive years, 1784-5, his re- 

 searches into the structure and economy of the Gorgonia verru-^ 

 cosa Lam., particularly with reference to the spontaneous mo- 

 tions and the development of its ova ; and his observations on 

 this animal form a model of patient and scientific inquiry, which 

 has no equal in the history of zoophytology. He examined the 

 position of the pvaria at the base of each polypus, watched the 

 manner in which the ova were discharged through eight small 

 oviducts, opening between the bases of the eight tentacula, and 



