may be procured, as well as the length of the period of 

 their free-swimming life. The larvae obtained by 1 5 rooks. 

 Rice, Ryder, Winslow, and others were obtained by cul- 

 ture from fertilized eggs, and were at most six days old, 

 and in the young straight-hinge stage. In Europe larvae 

 of a similar age, size and structure had been taken from 

 the infra-branchial cavity of the parent oyster by Da- 

 vaine, Lacaze-Duthiers, Coste, De la Blanchere, Gwyn 

 J effries, Saunders, Salensky, Mobius, Horst and Huxley, 

 but the older, later or larger stages were quite unknown. 

 This left room for some speculation as to the exact time, 

 place and manner in which the succeeding stages should 

 be found, as well as occasioned the prevalent mistake that 

 the free larva settles down at this period to become a 

 fixed spat. Brooks wrote. "All my attempts to get later 

 stages than these failed . . . and I am therefore unable 

 to describe the manner in which the swimming embryo 

 becomes converted into the adult, but I hope that tills 

 gap will be filled, either by future observations of my own 

 or by those of some other embryologist. " In a similar 

 way Jackson, at a later period, speaks of "a blank in the 

 knowledge of the development of the oyster." This 

 "gap" or "blank" is now completely filled. My studies 

 prove that the larva continues to live as a larva in the 

 sea-water about oyster-beds for two or three weeks 

 longer, where it swims about, feeds, grows and changes 

 in structure, and that it first settles down to become a 

 sedentary spat, fixed to shells or other objects, at an 

 age of three to four weeks from fertilization— the length 

 of time depending to some extent on temperature, food, 

 individuality or such causes. This information has been 

 gained through the method of procuring oyster-larva? 

 from the waters of oyster-areas by means of a plankton- 

 net, and connecting them in series with younger stages 

 obtained by fertilization and culture and with older 

 stages obtained by catching spat on glass, shells, etc., so 

 as to make out the complete life-history. 



The discovery that the hitherto unknown stages of the 



