70 
ZOOLOGY. 
When -^^ mm. {-^^ inch) in diameter it becomes fixed to a 
rock, and at the end of a year is capable of breeding. Oy- 
A 
Fig. 78. — -4, Venus mercenaria^ quohog, natural size, with the foot and siphons; 
Mactra (Mulinia) lateralis^ natural size. 
sters get their full growth by the second or third year. 
They breed from July to September. 
Fig. 79. — The Ship-worm, natural size, t, siphons; pallets; c, collar; s, shell; 
/, foot. 
The mussel (Fig. 77) has a small foot, with a gland for 
secreting a bundle of threads, the lyssuSy by means of 
