BULLETIN OF THE UNITED STATES FISH COMMISSION. 343 



RESEARCHES OIV THE GENERATIVE ORGANS OF THE OYSTER 



O. vdulis.)* 



By P. P. C. HOEK. 



Last year the administrative commission of the zoological station of 

 the Netherlands Society of Zoology took the initiative in the prosecu- 

 tion of researches relating to the anatomy, embryology, and biology of 

 the oyster. 



The anatomical portion of these investigations fell to my lot. My 

 work was done in a small wooden building, the station of the society, 

 which was in operation during the last two years in the vicinity of 

 Bergen-op-Zoom. This town, situated on the northernmost arm of the 

 Escaut, is also, so to speak, the center of oyster-culture in Holland. 



My investigations from the first have related to the generative organs 

 of the oyster. At the end of the first season I published a summary of 

 the work done, in the sixth annual report of the zoological station. Up 

 to the present time, after haviDg again devoted some months to these 

 studies, my results are so far developed that I publish herewith a sum- 

 mary of my investigations up to the end of the year. It will be pub- 

 lished simultaneously in French and Dutch. 



The most remarkable result of my researches during the past year 

 has been to learn that the generative organs do not consist of localized 

 glands, but that they extend over nearly the whole of the body mass; 

 and also that they do not correspond in structure to the usual defini- 

 tion of such organs (lobulated or botryoidal glands) usually met with 

 in lamellibranchiates. They are not separated on either side of the body 

 from the integument, which in these regions is at the same time the 

 mantle, consisting of a thin layer of connective tissue ; at the fore part 

 of the pericardiac cavity the dorsal and ventral portions, the right and 

 left halves of the organ are in communication. Everywhere we meet 

 with its branched ducts, which communicate with each other, and of 

 which the inner walls are produced into cul-de-sacs directed towards 

 the interior and vertically to the surface of the body. The epithelial 

 cells of these cul-de-sacs are metamorphosed into eggs as well as into 

 spermatogenetic cells. Therefore it is the same cul-de-sac which pro- 

 duces at one time spermatozoa and ova. 



The past year I had no luck in finding the generative openings. 

 With the exception of M. Laeaze-Duthiers all the authors who have 

 investigated this question have met with the same difficulty. To attain 

 better results than my predecessors, I had employed the method of sec- 

 tions; I isolated portions of the ventral process of the body mass, where 



* Recherche8 sur les organes genitaux des Huitres. Par M. P. P. C. Hoek. Comptes rendus 

 des seances de VAcademie des Sciences, Paris. Novembre 6, 1882. Translated by John A. 

 Ryder. 



