896 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 



the appearance of the embryos of the oyster when seen through the 

 microscope, and he gives some tolerably exact illustrations of them. 

 As it is possible to keep these larvj© alive, outside of the mother shell, 

 for several day^s, he thinks that this may become an important in- 

 dustry. 



De la Blauchere^" (1866) reports almost exactly the same as Davaine 

 and Coste. He also gives four good drawings showing larves of the 

 oyster, in which he shows the longitudinal muscles and the dorsal and 

 ventral muscles which cause the velum to be drawn back into the shell. 

 He says that, according to the observations of Mr. Gerbe, when the 

 larve of the oyster becomes properly defined, the velum dies, as the 

 branchise develop, so that it is probable that they have their origin in 

 this organ. 



Gwyn Jeffreys" (1869) observed the spawn of oysters when he exam- 

 ined an oyster fishery in the river Roach in Essex. He compares the. 

 larvae to the grains of seed of the shepherd's-pouch. He says that the 

 body can be seen through the transparent shell; the central portion is 

 opaque, almost black, and probably represents the liver. The front 

 part only is provided with vibratile cilia. 



Saunders^^ (1873) exhibited, at the session of July 10 of the East Kent 

 Natural History Society, live larvaj of oysters, and stated that they 

 have a small shell, the two valves of which are convex, while in the 

 grown oyster one is convex and the other flat. 



Salensky" (1874) gives in his Bemerkungen iiber Haeckels Gastrcea 

 theorie good illustrations of the three different i)hases of the develop- 

 ment of the oyster larvce. These illustrations serve as an example of the 

 development of the lamellibranchiates, which, according to him, have no 

 alimentary organ. The embryo is originally composed of two layers 

 without an internal cavity, and the intestinal cavity only makes its 

 appearance later in the eudoderm. 



Mobius (1877), in his charming little work, Die Auster imd die Austern- 

 wirthschaft, gives some illustrations of the first stages of the develop- 

 ment of the Oatrca ediiUs. He also gives a very accurate drawing of the 

 larva (with the adductor muscle); by mistake, however, this figure is 

 reversed, so that the velum is placed below. He found that the young 

 oysters leave the mother when they have reached the size of 0.15 to 0.18 

 millimeter. 



We must finally mention some reports regarding two other species, 

 namely, the American oyster [Ostrea virginiana) and the Portuguese 

 03'ster {Ostrea angulata). 



According to Brooks '* the American oyster (Ostrea inV^rmmnct List), 



10 H. de la Blanchfere: Industrie dcs Eaux, 1666, p. 69. 

 "British Concliology, vol. v, 1869, Supplement, p. 165. 

 '-'Quart. Jour. Microsc. Science, vol. xiii. 1873, p. 493. 

 ^■' ArcMv fu7- Naitirgeschichte, 1874, ^t, 150, Plate V, Figs. 1, 2, and 3. 

 '^ Studies from the Biological Laboratory of Johns Hopkins University, No. 4, Bal- 

 timore, ISdO, plates I-X. 



