63 



season of 1880, were much more satisfactory with half- 

 round tiles. Using hurdles or nests numbering 8 to 16 

 tiles, the results obtained from one placed in the Big 

 Annemessex were very flattering. After it had been im- 

 mersed 24 days 1506 oysters were counted ; after 45 days 

 1334 ; and after 93 days had elapsed the number still 

 adherent w^as 539. In size and at corresponding ages 

 these were similar to those which hxed themselves to the 

 slates used at St. Jerome' s. From what we know of the 

 number which sometimes fix themselves to a single object 

 we may 3^et look for great successes in the use of collect- 

 ing apparatus. In one instance, the inner face of one 

 valve of a dead oyster furnished attachment for over 40 

 spat from i to f of an inch in diameter. 



CHANGES OF FORM DURING THE GROWTH OF THE SHELL. 



N?-. 



—A* 



Figure 15. 



In Fig. 15 we have attempted to represent the changes 

 of shape and character of the shell of the oyster in pass- 

 ing from the free-swimming larval condition to that of 

 the adult. There are three well marked stages of shell- 

 growth, viz. : (1) the perfectly symmetrical stage attained 

 by the valves of the "fry ;" (2) the asymmetrical stage 

 of the "spat," and (3) the asymmetrical form assumed 

 by the valves of the adult. In the figure, wiiich is sup- 

 posed to be a section of the shell with all its parts pre- 

 served, cut through lengthwise from the hinge end to the 

 free edges of the valves, we note first, tliat the shells of 

 the larva or "fry" Is. are alike in cross-section ; tliat the 

 section of the "spat," wliich has affixed itself to a sta- 



