95 



BOYS AND GIRLS IN BIOLOGY. 



mussel will pull it in instantly and shut its doors. Re- 

 member we are still in the big chamber, and in the 

 same room, hanging down on each side of the foot, are 

 two striped-looking bodies, called gills (Fig. 93), one 

 lying a little over the other. The two outer ones are 

 fastened above to the mantle (Figs. 93, 94), while the 

 two inner ones are fastened at their top to the foot 



Fig. 94. 



Ventral Chamber. 



(Figs v 93, 94), and are joined together behind, making a 

 partition between the back-room and the large, family 

 sitting-room in front. 



Each room, or chamber, has its doors. The door 

 which leads from the front-room into the back-room 

 lies in front of the hindmost muscle, the posterior ad- 



