POLYPIFERA. 



59 



variety of motions which the gemmules are 

 capable of executing, were it not obvious 

 how complete is their control over the action 

 of the cilia, which are their sole locomotive 

 organs. They generally swim with the convex 

 part forwards, and with the greatest rapidity. 

 Sometimes they simply rotate upon their axis 

 or they tumble over and over, or, selecting a 

 fixed point, they whirl round it in rapid cir- 

 cles, carrying every loose particle after them. 

 Others creep along the bottom of the watch- 

 glass upon one end with a waddling gait; 

 but generally, after a few hours, all motion 

 ceases, and they are found to have attached 

 themselves to the bottom of the glass. At 

 the expiratioji of forty-eight hours the rudi- 



ments of a cell were observed extending be- 

 yond the margin of the body, but at this stage 

 the animals invariably perished, and Dr. Farre 

 had no opportunity of witnessing their further 

 metamorphosis.* 



Reproduction by ova. In the genus Pedicel- 

 Una Van Beneden discovered in most of the 

 individuals he examined, situated immediately 

 above the stomach, some rounded opaque cor- 

 puscles of a lactescent appearance (fig. 65, &), 

 which seem to be attached to that viscus ; 

 this he considers to be the ovary, containing 

 ova in various stages of development. In the 

 same situation he perceived an organ that he 



* Phil. Trans. 1837, p. 410. 



Fig. 65. 



Pedicellina 



A. Section. B. A group of individuals in various 

 states. The letters refer to each of the polypes, a, 

 mouth ; b, oesophagus ; c, stomach ; d, pylorus ; e, 

 intestine; /, anus; g, tentacular sheath; h, ten- 

 tacles ; i, oral disc ; k, ovum in the ovary ; I, 

 parietes of the polypary; m, stalk; n, superior, 

 and o, inferior, enlargement ; p, muscles of the 

 stalk ; q, intermuscular cellules ? 1. An adult 

 individual retracted into its cell, showing the 

 muscular fasciculi; r, sphincter; s, retractor; t, 



Belgica. 



oblique ; , v, animalcules accidentally attached to 

 the stalk ; 2, 3, 4, polypes in the act of expanding ; 

 5 6, 7, young individuals ; 8, buds in different 

 stages of development ; a, 8, very rudimentary ; 6, 8, 

 showing the cellule; c, 8, d, 8, a little more ad- 

 vanced ; e, 8, the embryo visible ; 9, the connecting 

 stalk; 10, an enlargement giving rise to several 

 buds; 11, tentacle magnified ; 12, a little group of 

 the natural size. (After Van Beneden.} 



