BULLETIN OF THE UNITED STATES FISH COMMISSION. 347 



meiit is attained at the lower side of the adductor muscle, just where 

 the posterior sickle-shaped column of white fibers comes iuto contact 

 with the larger grayish oval anterior column. Just in the angle formed 

 by these parallel muscular columns the organ is most massive, and 

 just here too lies the parieto-splanchnic ganglionic masses of nervous 

 matter, which are more or less enveloped by the external and perhaps 

 indifferent portions of the organ. 



As before stated, I have not taken the pains to demonstrate the open- 

 ing of the organ into the pericardiac cavity and the generative canals, 

 but as already hinted in my article in "Forest and Stream," which was 

 written before I had seen M. Hoek's paper, I believe such a connection 

 altogether probable from what is known of the relations of the homolo- 

 gous organs in other lamellibranchs. Just below the vicinity of the 

 thickest portion of the organ are situated the external openings of the 

 generative ducts, which, as observed by M. Hoek, are not marked by 

 papillar elevations. 



M. Hoek's observations on the generative ducts of Ostrea edulis agree 

 with my own on 0. virginica. From the openings of the ducts forward 

 over the sides and dorsal and ventral surfaces of the animal, beneath 

 the mantle-layer, they branch over the greater portion of the body- 

 mass, receiving the generative products from the underlying follicles, 

 which have a generally vertical direction, and stand at right angles to 

 the courses of the ducts and their ramifications. 



The sexual characteristics of 0. edulis, 0. angulata, and 0. virginica 

 have already been discussed by me in another essay which has preceded 

 this, so that there is no need of a further elaboration of that matter 

 here. More recently two notices by M. Bouchon-Brandely have been 

 placed in my hands by Professor Baird, which discuss this matter from 

 still another point of view than my own, viz, the microscopical and his- 

 tological aspect of the subject. 



Washington, D. C, December 25, 1882. 



A SIMPLE TEST TO LEARN IF FISH OVA ARE IMPREGNATED.* 



By PROFESSOR NUSSBAUM. 



The development of the eggs of game fishes [salmonoids], as is well 

 known, is relatively far advanced before the fish-culturist is positively 

 assured that embryos are developing normally in the egg. A method, 

 therefore, which would enable us to shorten this period of probation 

 would not only be desirable, but also of value under certain circum- 

 stances, since it is certainly annoying, after having had them in water 



* Ein einfaches Verfahren zur Erkennung der geluvgenen Befruchtung von Fischeiern, von 

 Professor Nussoaum in Bonn. Deutsche Fischer ei-Zeitung, VI, No. 5, Jan. 30, 1883. 

 Translated by John A. Ryder. 



