Professor Th. Bischoff in Reply to Dr. Martin Barry. 283 



individual points of cavil raised by Dr. Barry. I will here 

 notice one of them only, which is of too great importance to 

 be passed over in silence. 



It is known that Dr. Barry alleged that, in the zona pellu- 

 cida of the mature ovum, he had seen a fissure, and once in 

 it "an object very much resembling a spermatozoon." I have 

 at p. 31 of my memoir stated the reasons why I consider this 

 observation impossible. I then, at p. 32, proceed: — "I con- 

 sider it much more possible to decide the question by careful 

 examination of newly fecundated ova, whether a spermatozoon 

 really penetrates them or does not immediately become in some 

 manner dissolved. In the small ova of the Mammalia it will 

 perhaps be for the first possible to examine very accurately 

 the contents of the ovum for this purpose, and I have in many 

 cases directed my utmost attention to the point. It is to be 

 remarked that the ova in the Fallopian tube are always found 

 covered with numerous spermatozoa, a fact which Barry ap- 

 pears never to have observed, whereas I have done so more 

 than twenty times in a great number of ova. I, however, 

 never could satisfy myself that one of those spermatozoa was 

 contained in the interior of the ovum. I have indeed on two 

 occasions, whilst I crushed, with the compressorium under 

 the microscope, an ovum from the Fallopian tube, seen quite 

 distinctly a spermatozoon amongst the yelk granules which had 

 flowed out from the collapsed zona; and it appeared to come 

 out from the interior of the ovum. But as, as already said, 

 the ovum is covered all over with spermatozoa which are en- 

 closed in the layers of the albumen and are very difficult of 

 removal, deception is here very possible as well as probable. 

 Still this method is undoubtedly the surest, and with a suffi- 

 cient quantity of materials will certainly enable us to arrive at 

 certainty on the point, which appears to me impossible by pur- 

 suing the mode of investigation adopted by Barry." Dr. 

 Barry seems to have taken this hint, as he has now recently 

 communicated two observations, in which he alleges he has 

 seen spermatozoids in the ova in the Fallopian tube. He has 

 adduced Mr. Owen as a witness of this observation. The 

 above quotation from my memoir will secure me against being 

 supposed prejudiced against the entrance of spermatozoids into 

 the interior of the ova ; but it will at the same time show why 

 I consider Barry's alleged observation as still very doubtful. 

 As the albumen as well as the zona itself are transparent, a 

 very careful treatment of the object is required to convince 

 oneself whether the spermatozoids are situated on the zona 

 and in the albumen, or within the zona itself. We may en- 

 deavour to determine the point, partly by varying the focus of 



