C. M. CHILD. 



not capable of maintaining itself in an erect position in the water, 

 so long as it retains the elongated form (e. g., as in Figs. S-io). 

 The geotactic reaction usually manifests itself as in Cerianthus 

 by the bending of the body which lies on the bottom of the dish, 

 so that the disc lies in the horizontal plane and the axis of the 

 body immediately below it is vertical. The reaction proceeds no 

 further, apparently because the body is incapable of supporting 

 itself erect. This reaction is by no means universal : very fre- 

 quently it seems to be almost or wholly absent. Occasionally 

 individuals which are strongly contracted longitudinally are found 

 standing almost erect in the water, /. c., the body-wall is capable 

 under these conditions of supporting itself in the water. 



FIG. ii. 



FIG. 12. 



The decrease in average length continues from day to day in 

 water without sand, though of course with many fluctuations, as 

 the animal contracts or extends. After a week or two under 

 these conditions the animals usually resemble Figs. 11 and 12 in 

 shape. If the foot is attached, the aboral end is usually a flat 

 disc as in Fig. 12, if it is free, the body is usually a more or less 

 rounded sac without any visible demarcation of the foot-region 

 (Fig. 11). The attached individuals usually stand more or less 

 erect in water, and the unattached lie on their sides. In most 

 cases the free individuals lying on their sides show little or no 

 reaction to gravity, but the absence of the visible reaction is prob- 

 ably due merely to the fact that the stimulus is not sufficient to 

 induce bending of the column in its shortened condition. If 

 these individuals happen to become attached they often become 

 erect. 



