THE OVA OF THE SALMONIDiE. 3 



gress ; many of them have become opaque ; the majority of them, and those 

 which remain transparent, are of uniform appearance, whether seen with the 

 naked eye or under the microscope. Under a one-inch object-glass, in all of 

 them, at one spot, a patch, as it were of cellular tissue, is observable, seemingly 

 adhering to the membrane of the egg, with oil globules entangled in and sur- 

 rounding it. 



On the 2d December, I procured some eggs from two charr, taken at the same 

 time as the preceding, and from the same breeding shoal, and kept in company 

 with male fish in a well fed by a small stream. The eggs, obtained by pressure 

 to the abdomen, were the few remaining, the greater portion having been pre- 

 viously shed, as was manifest from the lankness of the fish. From this circum- 

 stance, they seemed peculiarly favourable for the trial, on the hypothesis of 

 the possible admission of the spermatic fluid db externo. But the result was 

 equally negative with the foregoing. The ova put into water, the same as that 

 used with the impregnated, fertile ova, and under the same circumstances, all 

 underwent no change, excepting that denoting loss of vitality. 



Many other instances of the like kind I could relate, that have been commu- 

 nicated by friends interested in the subject ; but I hardly think them necessary, 

 those I have given appearing to me so conclusive, even on the doctrine of chances. 



Next, it may be well to advert to the structure of the male and female of the 

 Salmonidse, to which I have alluded, as seeming to render impregnation from 

 without very improbable. 



The female, as it is well known, has no true oviduct, as in the instance of 

 the cartilaginous fish. Her ovaries are not connected with any permanent open- 

 ings; an aperture for their escape being made only just before the exclusion 

 of the ova, — that is, when the ova are mature and detached from the ovaries, and 

 when, by their volume, they distend and press on every part of the peritonaeal 

 sac, but necessarily with most effect where there is least resistance, viz., close to 

 the anus, the very spot where the aperture is to be formed with a suitable struc- 

 ture for their exit. How ill adapted is this for the required effect, according to 

 the supposition of impregnation of the ova before exclusion ? Moreover, as re- 

 gards the male fish, we see the same inaptitude exhibited in the conformation of 

 its generative organs. They are of the simplest kind, the testes terminating in 

 an aperture close to the anal end of the intestine, without even a distinct papilla 

 furnished with erectile tissue, and open only whilst needed for the outpouring 

 of the abundant spermatic fluid, distending the organs in which it is secreted, 

 and by them distending the abdomen. 



The inaptitude of the organs in both sexes for the presumed office is the more 

 manifest, as it has seemed to me, the closer the attention is given to the minute 

 structure of the parts concerned. In the instance of the female, the aperture is 

 in a vascular papilla, prominent at the verge of the anus, and internally pro- 



