C. M. CHILD. 



FIGS. 1-6. 



end from the surface, often 

 for a distance of several 

 inches, and usually more 

 or less complete invagina- 

 tion of the disc and tentacles. 

 As regards size and shape, 

 the same individual may 

 differ greatly at different 

 times, according to the de- 

 gree of distension with water 

 and of muscular contrac- 

 tion. In the condition of 

 extreme extension and dis- 

 tension, the larger individ- 

 uals possess approximately 

 the shape diagrammatically 

 outlined in Fig. I. 1 Fig. 2 

 represents a shape which is 

 perhaps nearer the average. 

 In general I have found 

 that the larger individuals 

 are not only absolutely 

 but relatively longer than 

 the smaller. Apparently 

 growth, at least in those 

 later stages of development 

 which I have observed, is 

 chiefly in the longitudinal 

 direction. But the length 

 differs considerably accord- 

 ing to external conditions. 

 In certain regions I found 

 the animals living in soft 

 sand which was underlaid 

 at a depth of 20-25 cm. 

 by a layer of broken shells. 

 Under these conditions the 



1 Figs. 1-6 are somewhat less than one half natural size ; other figures are about 

 three fourths natural size. 



