49. 



all of tiie specinens examined, seem to imdergo ohan/^es that result 

 in tlie formation of large cells, figures 35, 64, and 65, Z, that 

 are not arranged in any definite manner. 



It was thouglit possible that tJais appearance was due to 

 poor preservation, an explanation that -veirj naturally suggests 

 itself, but the large cells appear in living as well as preser^red 

 specinens. Reformation of the liver pouches is accompanied by 

 the disappearance of these cells. 



The anterior adductor muscle soon becomes enclosed lij 

 the forward growth of the bods'". For a few hotii's a space may re- 

 main between it and tl-ie cerebral ganglia but this soon disappears. 

 The foot, which at first is capable of onlj'- feeble movements, 

 grows quite rapidly, and is soon ver;'- active. Locomotion is 

 chiefly effected by the means of long and powerful cilia, ^.ich 

 are arranged along the sides of the foot, figures 35, and 36, and 

 are very active whenever the foot is tiirust oixt of the shell. 



These enable the animal to glide over the surface on 

 which it lies, but do not enable it to rise. For some hours 

 after the test is cast, the foot shoiws no indication of the modi- 

 fication which is later generally knovjn as the sole, figure 52. 

 The first indication of this modification is a groove vfiiich ap- 

 pears along the middle line of the ventral surface of the foot. 



