30 COMMISSION OF CONSERVATION 



development and activity. From this period onwards it becomes next to 

 impossible to keep specimens alive, which is doubtless principally due to 

 the difficulty of supplying them with suitable food without injuring or 

 losing them. 



Rice (18S5 p. 116) stated: " The first efforts in this country in the direction of arti- 

 ficial propagation were made by the writer in the summer of 1S78 in conjunction with 

 Dr. W. K. Brooks, but these experiments were not successful. The next season, how- 

 ever, Dr. Brooks succeeded in impregnating the eggs and raising the embryos until they 

 were six days old, when they all died for lack of fresh water, as Dr. Brooks was unable to 

 arrange any apparatus which would admit of a current of water through the breeding 

 vessel that would not allow the young oysters to escape." 



Brooks (1SS0 p. 25) wrote: "The stages shown in figures 44 and 45 agree pretty 

 closely with the figures which European emb^ologists give of the oyster embryo at the 

 time when it escapes from the mantle chamber of its parent. The American oyster 

 reaches this stage in from twenty-four hours to six days after the egg is fertilized 

 All my attempts to get later stages than these failed, through my inability to find any 

 way to change the water without losing the young oyster, and I am therefore unable to 

 describe the manner in which the swimming embryo becomes converted into the adult, 

 but I hope that this gap will be filled, either by future observations of my own or by 

 those of some other embryologist." 



Winslow (18S2 p. 757) "Our observations at Beaufort showed us that after the 

 embryos had once developed the shell to any extent there was little motion of trans- 

 lation, the animals remaining quietly in one place at the bottom. Indeed their 

 specific gravity at this period, together with their deficient locomotive powers, should 

 prevent any very rapid or extensive movements the oyster embryo is pre- 

 disposed at least to fix itself very soon after the process of segmentation is completed." 



Horst (1882 p. 165) " Older stages than that represented in fig. 12 I was unfortu- 

 nately not able to investigate, so that regarding the length of the period which inter- 

 venes between the time when the larvae are set free, and the time at which they fix 

 themselves, as well as the changes which they undergo during this period, lam unable 

 to affirm anything." 



Rijder (1882-3 p. 328) "Fig. 1 in the accompanying Plate LXXV, which repre- 

 sents a young American oyster in the larval or fry stage enlarged 250 times" (In the 

 description of the plate he stated "enlarged 183 times.") "The duration of the loco- 

 motive stage of development of the larva has not yet been certainly determined for any 

 one of the three species of which the development has been studied." 



Huxley (1883 p. 53) "How long the larval oysters remain in this locomotive state 

 under natural conditions, is unknown, but they may certainly retain their activity for a 

 week, as I have kept them myself in a bottle of sea-water, which was neither changed 

 nor aerated for that period." 



Horst (1884 p. 904) "The larva represented in fig. 16 is the most advanced stage 

 of free larva which we have observed; this had been taken from the mantle cavity of the 

 mother oyster, or had been ejected by it when placed in an aquarium. I am not able 

 to say anything positive in regard to the duration of the period which elapses from the 

 time when the larvae become free to the time when they become fixed; nor do I 



know what changes they undergo during this period At first the shell 



grows very rapidly, for while it only measures 0-16 millimeters in height in a larva 

 which is on the point of leaving the mother oyster, it measures more than 0-24 milli- 

 meters in the smallest of the fixed shells." 



Ryder (1884 p. 727) "Our experiments made at St. Jerome creek during the 

 past summer gave the most contradictory results, and the interval of development be- 

 tween that of our oldest embryo with its diminutive Pisidium-like valves measuring 

 about 1/500 inch in diameter and that of the embryo when its valves first begin to lose 

 their embryonic form, still remains unbridged. The dimensions of the embryo or fry, 

 as we may more properly call it when it becomes fixed, are between 1/80 and 1/90 inch 

 according as the measurement is made longitudinally or transversely. The difference 

 in magnitude between the oldest artificially incubated fry seen by me and that of the 

 youngest fixed embryo which I collected is very small, amounting only to 41/4500 inch, 

 or a little more than 1/109 inch." 



Rice (18S5 p. 115) "The attachment takes place in about two days from the time 

 of fertilization." 



Jackson (1890 p. 300) " Between the stage fig. 25, and our next stage, Plate XXIV, 

 figs. 1-2, there is a blank in the knowledge of the development of the oyster. It has 



