[ ol2 ] 



Preliminary Account of a Contribution to an Evaluation 



of the Sea. 



By 

 J. H. Orton, B.Sc, A.R.C.Sc, 



Nahiralist at the Plymouth Laboratory. 



TABLE OF CONTENTS. 



Introduction ......... 



Rate of Growth in some Coelenterata .... 



Rate of Growth in some Porifera and the Hfe-history of Sycon, Grantia, 

 solenia ......... 



Rate of Growth m some Platyhelminthes .... 



Rate of Growth in some Annehda ..... 



Rate of Growth in some Polyzoa ..... 



Rate of Growth in some Crustacea ..... 



Rate of Growth in some MoUusca ..... 



Rate of Growth of Crepidula fornicata .... 



The age of sex-change m C. fornicata .... 



Rate of Growth of Oyster spat in the first summer 



The life-history of Galvina picia ..... 



The life-history of Ciona, Clavellina, and Ascidiella 



Rate of Growth in some other Tunicates .... 



Rate of Growth in Saccorhiza hiilbosa .... 



Summary ......... 



and 



Leuco- 



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INTRODUCTION. 



An investigation of the ra,te of growth in Marine Invertebrates was 

 begun in 1911, and a large amount of material the age of which is known 

 has now been collected from various sources. The particular objects of 

 this research are : (1) to establish the age of common marine inverte- 

 brates, (2) to determine the minimum age at which these forms begin to 

 breed, (3) to examine the rate of growth at different seasons of the year 

 and under different conditions, (4) to investigate the fecundity of difierent 

 forms so far as possible, and (5) to collect the scattered literature on 

 these subjects. 



The investigations have been carried on mainly by immersing various 

 objects in the sea at a known time and subsequently observing and collect- 



