197 
the end of that month, as far as I could ascertain the condi- 
tion of both ova and spermatozoa depended upon the depth 
■of water, though the rule was not invariable. 
The generative products of the deep water oysters reached 
a state most favorable for reproduction several weeks after the 
same had occurred in the shoal water ; and, in general terms, 
neither ova nor spermatozoa in most of the oysters in either 
deep or shoal water after the middle of August was in a state 
favorable for fertilization. 
Large numbers of oysters in all depths passed through the 
spawning season without expelling the contents of the genera- 
tive organs. I found this the case especially on the beds on 
■the western side of Tangier Sound, above Kedge’s Straits, 
where, on the 8th and 9th of October, we found many oysters 
fattening with the generative matter unexpelled. I was in- 
formed that this was not unusual, and that it injured the oys- 
ter for marketable purposes. 
As late as the 8th I found oysters with the generative mat- 
ter in good condition, and on the 7th of October I succeeded 
in securing from oysters taken from Kedge’s Straits a suffi- 
cient amount of ova and spermatozoa to make experiments in 
artificial impregnation, and was successful in producing one 
embryo oyster. 
Probably had I used greater care a larger number would 
have resulted. 
During the season of 1878 we observed large numbers of 
ustyris in the shells of the mature oysters, and attached to 
those of the young. In many cases they were found in the 
holes which had been bored in the shells of the latter. 
As we could not find any known enemy of the oyster in 
sufficient numbers to account for the evident damage done, 
and as so many circumstances pointed to the astyris as the 
cause, I concluded that the boring must be done by that ani- 
mal, and alluded to it in my previous report. The specimens 
preserved were described by Mr. W. H. Dali, and the descrip- 
tion appended to that report. 
During the past summer we have found a much larger num- 
ber of the rough welks ( urosalpinx cinereus) than during the 
