208 
The influence of increased or diminished temperature upon' 
the formation of the ova and spermatozoa must be very serious 
and very considerable, and, judging by analogy, it would seem, 
probable that the formation would be more rapid during a 
warm spring than during a cold one. 
Whether the formation has been late or early when once 
formed, a sudden change of density or of temperature may so 
affect the oyster or the generative matter that the latter would, 
not be expelled, and only upon this hypothesis can be ex- 
plained the retention of the products of generation noticed in 
so many oysters, and which is said to be so common, for none 
of the other conditions are subject to violent changes, such 
being peculiar to the density and temperature alone. 
Prof. Brooks states that he found both ova and spermatozoa 
ripe and fit for fertilization about the middle of May, and as 
the oysters were taken from shoal water, probably one fathom 
deep, the shoal water oysters were probably spawning through- 
out June. Both Prof. Brooks and myself found the ripeness 
of the oysters to depend upon the depth of water from which 
it was taken, and this is no doubt caused by the difference of 
temperatures. 
Prof. Brooks also states that there was a great deal of cold, 
rainy weather during June, and two hail storms. The rainy 
weather would affect the density of the water by increasing 
the volumes of the various creeks and rivers, and the changes 
of density would probably affect the production and emission 
of the generative matter. 
It is an interesting coincidence at least, that the oysters found 
to be fattening with the products of generation unexpelled 
were either from beds in comparatively shoal water or from 
the shoal parts of deep w T ater beds, and that those oysters 
should have been ripe and spawning during the month of 
June. Again, it may be that the lowness of the temperature 
prevented the deep water oysters from ripening as soon as 
usual, and the mildness of the succeeding autumn may have 
prevented the destruction of the ova and spermatozoa, thus 
rendering possible the fertilization achieved by me in October.. 
The oysters from which I procured the ova and spermatozoa 
were taken from deep water. 
