BULLETIN OF TIIE UNITED STATES FISH COMMISSION. 103 



Vol. V, TVo. IS. Washington, 1>. C. Aug. 11, 18N5. 



*7.-t!OHPABATIVE EXAMINATION Of CULTIVATED AND UNCULTI- 

 VATED OYMTEKS, WITH TIIE VIEW TO DETERMINE THE NUM- 

 BER WHICH, DURING THE I'JKST VE ABC, TOOK PART IN REI'RO 

 DUCTION." 



By Dr. P. P. C. nOEK. 



I have already mentioned in this report that iu nty investigations of 

 the genital organs of the oyster I bad not hud an opportunity to ascer- 

 tain the number of individuals which produce young ones during the 

 first year. At the same time I advanced the opinion that it was very 

 likely possible that iu this respect there was a noticeable difference 

 between cultivated and uncultivated oysters. 



Baron Groeninx van Zoelen and Baron G-.-H. Clifford, oyster cultiva- 

 tors on the East Schelde, after reading my statement, offered me a suffi- 

 cient quantity of oysters of both kinds for making comparative studies. 

 This offer, which was particularly agreeable to me, and which I could 

 not appreciate too highly, was eagerly accepted by me. Toward the 

 end of June, 1883, 1 received 200 oysters from a locality where cultivated 

 oysters had uninterruptedly been planted for a number of years ; and 

 also 200 oysters gathered in waters t belonging to an oyster region 

 which they had rented for years, but where no oysters had ever been 

 planted. I confined my investigations to these 400 oysters, although 

 more were offered me. In my opinion a larger number — say 800 — 

 would not have formed a more reliable basis for my conclusions ; and, 

 moreover, my time was too limited to extend these investigations very 

 much. They have, therefore, only a comparatively small value as re- 

 gards the comparison between cultivated and uncultivated oysters. I 

 nevertheless determined to publish the results of my investigations, 

 because I deem it important to ascertain exactly the condition of the 

 sexual organs of a certain number of oysters at the beginning of the 

 period of reproduction. 



I am by no means the first to appreciate the importance of similar in- 

 vestigations, nor am 1 the first to make them. Not to go back to older 

 authors, I must refer to Mr. Gerbe £ and Professor Mobius. Mr. Gerbe 



* " Vergelijkend onderzoek van gekweekte en in het ivild opgegroeide" oesters, ingesteld ter 

 bepaling van het aantal dat per jaar aan de voortplanting deelneemt. From Tijdschrift der 

 Nederlandsche Dierkundige Vereeniging, Supplement No. 1, Leyden, 1683-84. Trans- 

 lated from tbe Dutch by Herman Jacobson. 



t These waters are called ' ' Geul ; " tbey are situated nortbeast of Yerseke, and their 

 depth is about 33 feet. 



}Z. Gerbe: "Aptitude qu'ont les haitres de se reproduire ties la premiere anne'e," in 

 Eevue $ Mayas, de ZooJogie pure et appliquee, 3d series (Gue'rin-Me'neville, Paris), IV, 

 1876. 



Bull. U. S. F. 0., 85 13 



