FECUNDATING THE OVA OF THE SALM0NIDJ5, ETC. 87 



Piscator replies (p. 142): — "I have made many experiments 

 on tlie subject, as have others, and the results have been all 

 negative. In no instance that the mature ova have been isolated 

 after exclusion, have they proved fertile, unless milt were added. 

 In the case recorded in the newspapers, in which young Trout 

 were said to have been obtained from ova placed in a perforated 

 box in a stream, we cannot be sure that they were isolated ; the 

 diffusible mature milt, shed by a male above, might have been 

 conveyed to them in the running water. Moreover, the or- 

 ganisation of the fish exliibits a total inajDtitude for the mode 

 of impregnation imagined. If curious on the subject, I may 

 refer you to a paper expressly on it, published in the last volume 

 of the ' Transactions of the Royal Society of Edinburgh ; ' " and 

 from which some passages have been already quoted. 



In conclusion, I ought to explain that the expressions which I 

 have used in this paper — namely, the " vivifying influence of the 

 male semen of animals," and the "fecundating principle," or 

 "influence of the milt," or "of the male" fish, indicate the 

 seminal animalcules, or spermatozoa — which are doubtless the chief 

 objects or natural instruments in fecundating the ova. And it 

 seems now to be settled that these spermatozoa, in some cases 

 forcibly enter through any part of the enveloping membrane 

 into the interior of the ovum, and in others through a peculiar 

 small orifice termed micropyle^ from its resemblance to the micro- 

 pyle of the ovule in flowering plants. Barry, Loven Nelson, 

 Leuckart, Johann Miiller, and Keber, I believe are among the 

 first who have determined this micropyle; whilst Von Baer, 

 Bruch, and Ransom,* with others, have noticed it in the roe, 

 or ova, of several kinds of fresh-water fishes. 



• Whilst this paper was going through the press. Dr. Ransom stated in a letter to 

 me, dated November 24th, 1856, "You will find in the last part of the 'Cyclopsedia of 

 Anatomy and Physiology,' article Ovum, several of my observations, and a very com- 

 plete resume of the whole subject, as also a reference to Von Baer, and other early 

 observers." (J. H., January 29, 1857.) 



VOL. III. PT. IT. 



