[3] OYSTER CULTIVATION IN THE NETHERLANDS. 1003 
taining their sections for microscopic observations. Oysters can be 
hardened by means of different liquids; as far as our experience goes, 
we are inclined to give preference to pure alcohol or combinations of 
chromium. 
The results which have so far been reached, and which, from their 
nature, must be considered as preliminary, are given below. Although 
it would perhaps be preferable not to publish some of these supposed 
results, as yet, we shall give them, so that they may serve as guides in 
future investigations : 
(1.) The generative organ of the oyster is not, as in other lamellibran- 
chiates, a strictly localized organ, but extends equally on both sides of 
the body. The organ on the right side is connected with that on the 
left, both on the abdomen and on the back, and besides this by a por- 
tion which bounds the pericardial cavity in front. It is therefore a con- 
tinuous organ which does not extend into the mantle. 
(2.) The generative organ is located near the surface of the body, but 
is separated from the skin by a thin layer of tissue. 
(3.) The generative organ consists of a system of vessels which, 
throughout, have an anastomotic character, and which run parallel with 
the surface of the oyster, and from their internal sides or faces there 
arise blind tubular prolongations which extend inwards into the tissue 
of the body. In these tubes the generative products are developed. 
(4.) The generative products are developed from the epithelial cells, 
which cover the inner sides of these blind tubes or follicles. During this 
process both male and female generative products are developed close 
to each other in one and the same follicle, and can gradually be distin- 
guished from each other by their structure and the manner in which 
they color. 
(5.) It must be considered as a rule, that one of the two generative 
products in one and the same oyster will, in its development, by far ex- 
ceed the other. Those generative organs which furnish principally 
male products, contain but few eggs, and these in a very backward 
state; whilst in those organs which furnish principally female products, 
the male products appear to be still less developed than the female pro- 
ducts in the first mentioned case. 
(6.) The generative organs of an oyster, having young spat in its gills, 
appear in sections as large vacant spaces. Whilst in such oysters nearly 
all the eggs had disappeared from the follicles, the male products were 
much more developed than had been observed in some principally female 
oysters, during the period that the eggs were still in the follicles. This 
observation seems to favor the opinion that the same follicles develop 
first eggs and then spermatozoa. This, however, does not prove that 
the reverse cannot also be the case. 
(7.) The opinion advanced by Lacaze-Duthiers, that all the blind tubn- 
lar acini or follicles of the generative organ, on both sides of the body, 
pour their contents into a main channel, having an opening on each side 
