1004 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [4] 
near the surface of the body, located under the mantle on the ventral 
side of the large muscle, rests on a mistake. 
(8.) Rolleston’s and Robertson’s opinion, that lymphatic vessels occur 
in Lamellibranchiates, deserves to be carefully examined. There are, 
in the oyster, vessels, the inside of which is coated with a layer of cells 
with small cilia. These may be observed especially in both sides of the 
pericardial cavity. Occasionally specimens are obtained in which they 
can only be distinguished from the anastomosing vessels, on the internal 
aspect of which the generative follicles are found, by the greater length 
of the hairs. In some specimens such a supposed lymphatic vessel, ac- 
cording to the view of Rolleston and Robertson, may be observed, one 
side of which is coated with young eggs. 
(9.) It is improbable that the organ of Bojanus has anything to do 
with the emission of the generative products. Nothing is known eon- 
cerning such an organ in the oyster; but everything which relates to 
the determination of the anatomy of the generative organs of the oyster, 
should be carefully observed. It is found on the ventral side of the 
pericardial cavity and communicates with it through a narrow slit, al- 
most a distinct papilla. In sections of this organ cecal tubes may be 
observed, the yellow and peculiarly formed cells of which are highly 
characteristic. 
(10.) It may be considered as absolutely certain that the eggs are im- 
pregnated by spermatozoids from another oyster; but it cannot as yet 
be said with certainty whether these spermatozoids reach the eggs at 
the very moment they are emitted, or whether this takes place in the 
generative follicles or in some of the vessels. Whenever an oyster has 
eggs between her gills, all that can be said with absolute certainty is 
this, that these eggs have been produced by that oyster. 
Dr. Vasmaer offered the following report of his observations relative 
to the natural history of the oyster: 
Owing to the nature of the case the following observations can only 
be regarded as implied by their title, as a report of my activity. It would 
be unjust to look at present for important results. 
After having microscopically examined a number of large oysters, in 
order to get a general idea, I soon became convinced that success could . 
only be looked for from microscopic observations. The method now 
so much in vogue of making a series of sections or slices, in order to 
obtain a clearer insight into the structure of the animal, will doubtless 
throw light on many dark points. Although I am sorry to say that I 
am not yet able to state where the generative vessels empty, I feel con- 
vinced that a series of sections will lead to some certainty in this mat- 
ter. It is certain, however, that the opinions of Lacaze-Duthiers and 
those who have followed him are not correct. 
Firmly convinced that the method referred to is preferable to all 
others, I have not only made numerous sections of small oysters, which, 
therefore, in their entirety, could be subjected to microscopic observa- 
