THE CLAVIFORM POLYPES. 33 



there issues from it an oval somewhat elongated embryo, 

 (fig. 53 a, and 54,) the whole of whose surface is covered 

 with cilia, by which it is enabled to move about in the 

 water in all directions, whilst at the same time it con- 

 tracts and elongates its body, which is sometimes more 

 of an oval or even pear-shaped form, and sometimes longer 

 and attenuated posteriorly. Loven distinguished in this 

 embryo, an interior cavity, containing an opaque fluid, 

 and CKCumscribed by two membranes, of which the 

 internal is opaque and the outer one as transparent as 

 glass. He was unable to discover any oral orifice, and it 

 is hardly probable that one should be formed at this 

 stage of development. 



After swimming about freely for some time, the little 

 creature attaches itself to any large object, as the frond of 

 a fucus, becomes contracted, and assumes a circular 

 figure. The cilia cease to vibrate and the membrane 

 upon which they are situate forms a narrow, nearly trans- 

 parent border around the animal, in the centre of which 

 an opaque spot is visible, which is formed by the close 

 aggregation of the minute granules contained in the 

 fluid (flg. 55.) Over this opaque spot the surface becomes 

 slightly elevated into a rounded projection ; this is the 

 commencement of a polype stem, which rises graduaUy 

 in a vertical direction from the circular, expanded disc, 

 the substance of which contracts at the same time, and 

 is divided into four lobes (fig. 56,) which, according to 

 Loven, are the first traces of the offsets most usuaUy put 

 out from the stem of the polype. By the alternate ad- 

 vance and stopping of the growth, the circular con- 

 tractions are caused which give its annulated aspect to 

 the stem of the polype. Fig. 57 shows the stem at the 

 beginning of its growth ; its internal cavity, filled with 

 the finely granular fluid which circulates within it (which 

 may not inappropriately be compared to a nutritious 

 matter or chyle,) rises in a conical or spherical form, dis- 

 tending its two containing membranes. The convex 

 surface of the external membrane secretes a delicate epi- 



3 



