Bull. U. S. B. F., 1921-22. (Doc. 922.) 



METRIC 



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189 



190 



192 



,91 ,93 



Fig. 189. — Growth stages of young mussels which collected on the rope of a fish trap put out 

 in Buzzards Bay near Woods Hole. Mass.. in April and taken up the last week in August. The 

 largest individuals were nearly three-fourths of an inch lone and could not have been more than 

 4 months old. 



Figs. 190 and 191.— Side views of young mussels showing amount of growth, indicated by 

 area outside the light colored growth line, which took place in transplanted specimens at More- 

 cambe, England, during a period of seven months.. (After Bjerkan. 1911-) 



Figs. 192 and 19).— Lateral and dorsal views of an old mussel showing growth, indicated by 

 the new shell area, that was stimulated by transplanting after it had remained almost stationary 

 in size for years. (After Bjerkan, 1911.) 



