70 



ZOOLOGY. 



When T 3 7 mm. (^g- inch) in diameter it becomes fixed to a 

 rock, and at the end of a year is capable of breeding. Oy- 



A 



Fig. 78.— A, Venus mercenaria, quohog. natural size, with the foot and siphons; 

 B, 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 Sliip-worm, natural size, t, siphons; p, pallets; c, collar; s, shell; 



/, foot. 



The mussel (Fig. 77) has a small foot, with a gland for 

 secreting a bundle of threads, the lyssus, by means of 



