No. 505] THE CANADIAN OYSTER 



43 



2. They may be taken in a plankton net at the surface 

 and at various depths. 



3. All stages from the freshly fertilized egg to the 

 full-grown larva must be there. 



4. The free-swimming period is, perhaps, considerable, 

 close on a month. 



5. They feed and grow, while in the free-swimming 

 state, through a straight-hinge to an umbo-stage. 



6. Normal fixation takes place when the larval shell 

 is about .38 m. in length, and then the spat period begins. 



7. A metamorphosis occurs through loss of larval or- 

 gans as velum, foot, eye-spot, otocysts, etc., and a develop- 

 ment of new organs as spat-shell, additional gills, palps, 

 etc., is begun. 



8. The larval shell is asymmetrical, as is also to some 

 extent the contained body. 



9. A foot, homologous with that of mollusks in general, 

 is present in the older larvas. 



10. The otocysts contain otoconia. 



11. Pedal ganglia are present. 



12. A byssus-gland is present. 



13. Gills are present. 



14. Eye-spots are present. 



15. A rigid system of measurements has been used, 

 and a comparison of actual sizes at different periods of 

 growth introduced. 



16. Numerous niceties of structure, shape, color, ac- 

 tivity, time, place, etc., are noted. 



17. The spawning period has been limited. 



18. Attention is directed to the importance of these 

 theses and observations as bearing upon problems and 

 methods of oyster culture. 



European works referring to the development of the oyster larva are 

 those of: 



1. 1854. Lacaze-Duthiers. Mem. sur le develop, des Acephales Lamellibr. 



Comptes Rendu* htb. tl< s Stances de I' Acad, des Sciences, 



2. 1882 ('83). Horat. A Oontrib. to our Knowl. of the Develop, of the 



