64 FISH—-CULTURAL ASSOCIATION. 
plished to the extent of thousands of millions ; and should it be 
found possible to keep these hosts of young alive until they had 
passed certain critical periods of their embryonic existence, we 
would have practically succeeded in adding so many millions 
of spat to those already existing, from which seed might be sup- 
plied for the foundation of extensive beds where oysters had 
been previously unknown. 
Brooks, in carrying embryo oysters up to the sixth day of 
their existence, encountered the same difficulties as those who 
have repeated his experiments. If, as I have good evidence for 
premising, when the young oyster ceases its wandering habits, 
its valves measure one-eightieth of an inch in their longest diam- 
eter, we have yet to find out how old it is when of this size. 
When we learn this, we will know how long it will be necessary 
for us to keep the young in the incubating apparatus. We can 
reach the answers to these questions only by the use of the pro- 
per sort of hatching arrangement, in which artificially impreg- 
nated eggs are used ; being careful, of course, to keep accurate 
records of the time of impregnation and the fluctuations of tem- 
perature of the air and water during the progess of the experi- 
ment. Facilities for the fry to fix itself may be provided by 
suspending strips of mica or glass in the water, watching the 
result from day to day, and as some are seen to have attached 
themselves, the transparent slips may be transferred to the stage 
of the microscope for examination to learn the nature of the 
attachment of the embryo. 
With the finer questions of the anatomy of the embryos we 
have little to do—in fact,I do not see that they will help us 
much in the comprehension of how the hatching process is to be 
conducted, which goes without saying, however, that the ex- 
perienced embryologist must be expected to determine whether 
the development is progressing normally and healthfully. When 
once we have achieved what has been indicated above, the em- 
bryologist will have an abundance of opportunity to make out 
the finer details of structure ; and let us remark here, in regard 
to the oyster, one of the most accessible of animals, that much 
still remains to be done by both the anatomist and embry- 
ologist. 
