[31]. —s« THE OYSTER AND’ OYSTER-CULTURE. 113 
oyster has thus not changed during the course of at least ten thousand 
years. It has not accommodated itself to the changes which have taken 
place in the territory occupied by it, but has yielded to those changes, 
although they were brought about very slowly.’ Hence it is impossible 
for any human power to change their nature in a short time and accus- 
tom them to the water of the Baltic as it is to-day. 
The following Danish works treat of the oyster-beds of the Lim Fiord, 
the extension of the oyster into the southern portion of the Cattegat, 
and of the unsuccessful attempts to plant oysters in the Baltic: 
Jonas Collin. Om Ostersfiskeriet i Limfjorden. (With a chart of the oyster-beds. ) 
Copenhagen, 1872. 
G. Winther. Om vore Haves Naturforhold med Hensyn til konstig Ostersayl og om 
de i den Henseende anstillede Forség. Copenhagen, 1876. 
F’. Krogh. Den konstige Ostersayl og dens Indférelse i Danmark. Hadersleben, 
1870. 
In the royal archives at Stettin and Stralsund are to be found the acts under which 
the attempts to locate oysters along the coast of Pomerania in 1830 and 1843 were 
made. 
9.—SIZES AND PRODUCTIVENESS OF THE OYSTER. 
The delightful hopes of bordering the entire German sea-coast with 
fruitful oyster-beds, and of seeing German oysters as food upon every 
table, must, therefore, be given up. The nature of our waters, as well as 
the nature of the oyster itself, forces us to do so. Yet it is especially 
difficult for those to understand this who share the widespread opinion 
that all eggs which are spawned by oysters are destined to become trans- 
formed into young mollusks. Most animals, however, whose ova and 
young are exposed to attacks and liable to be destroyed, produce a large 
number of eggs, while those animals, on the contrary, which guard their 
broods until they can take care of themselves, as is the case with mam- 
mals, birds, and some invertebrates, generally produce but few eggs ; but 
in those cases where care for the brood is entirely lacking, or lasts for a 
very short time only, eggs are produced in such great numbers that the 
numerous enemies Which regularly attack them are not able to destroy 
them all. <A certain number escape destruction and arrive at maturity. 
The tape-worm of man (Tenia solium) produces from its eight hundred 
segments not far from forty million germs, and the parasite Ascaris 
lumbricoides forms in its ovary about sixty million eggs. ¢ Under the 
normal condition of affairs for the development of these worms, only 
a very few of the great number of eggs laid ever go so far in growth 
that they in turn produce eggs. This is satisfactory to everybody, since 
none desire that all of the forty million eggs of the tape-worm or the 
sixty million eggs of the “‘itch-insect” should ever become mature para- 
sites. It would be a horrible state of affairs if such a thing should hap- 
pen. On the contrary, every one very much desires that all the young 
broods which the oyster sends forthinto the water should become ma- | 
ture table-oysters, since, when fully grown, they become one of the most 
