ZOOPMYTA ASTKROIDA. 173 



and alter their form. " When placed under the microscope," 

 says Professor Grant,* " and viewed by transmitted light, they 

 appeared as opaque spheres surrounded with a thin transparent 

 margin, which increased in thickness when the ova began to grow, 

 and such of the ova as lay in contact united and grew as one ovum. 

 A rapid current in the water immediately around each ovum, 

 drawing along with it all loose particles and floating animalcules, 

 was distinctly seen flowing with an equal velocity as in other ci- 

 liated ova, and a zone of very minute vibrating ciliae was per- 

 ceptible, surrounding the transparent margin of all the ova. The 

 progressive motion of the ova, always in a direction contrary to 

 that of the current created by their cilise, was very obvious, 

 though less rapid than in any other zoophyte in which I have 

 observed the same remarkable phenomenon. The specimen 

 suspended in a glass jar filled with pure sea- water I now brought 

 so close to the transparent side of the vessel, that I could ex- 

 amine through it, with the assistance of a powerful lens, and 

 without disturbing the animal, the motions and progress of the 

 groups of ova passing through the colourless bodies of the poly- 

 pi. To the naked eye at first sight all appeared motionless. 

 The deep vermilion hue of the small round ova, and the colour- 

 less transparency of the outer covering of the polypi, formed a 

 beautiful contrast with the pure white colour of the delicate 

 longitudinal folds, the central open canal, and the slender fila- 

 ments which wind down from its sides towards the clusters of 

 white ova at the base ; but the living phenomena discovered 

 within were even more admirable than the beautiful contrast of 

 colours, the elegant forms, and the exquisite structure of all the 

 parts. When observed with a lens the ova were seen to be in 

 constant motion, and quite free within the bodies of the polypi. 

 They moved themselves backwards and forwards, and frequent- 

 ly contracted their sides, as if irritated or capable of feeling. I 

 could observe none passing upwards between the stomach and 

 the sides of the polypi. They never assumed the appearance 

 of a string of beads inclosed in a narrow shut curved tube, as 

 represented by Spix, but swam freely in the water which dis- 

 tended the polypi, as figured by Ellis. Their motions in the 



* Dr Grant's observations, quoted in tlif text, were made on Alcyonium di- 

 gitatum, but the generalities may be safely applied to the other families, agree- 

 ing as they do with the observations of Cavolini on Gorgonia. 



