212 
MR. NEWPORT ON THE IMPREGNATION OP 
5. NATURE OF THE AGENCY OF THE SPERMATOZOA. 
Having obtained full evidence by direct experiment that impregnation is effected 
through means of the spermatozoa, we have now to inquire as to the manner in 
which it is induced by them, and as to the nature of the agency they exert. Sperma- 
tozoa have been found adhering to the surface of the impregnated ovum by Barry, 
Bischoff, Pouchet and others, in the Mammalia; as they were long ago seen by 
Prevost and Dumas on the ovum of the Amphibia ; and since by Siebold, Kolliker, 
myself and others in the Invertebrata. They have been constantly present in those 
experiments on artificial impregnation which I have now detailed, in which the yelks 
became segmented after the egg had been in contact with seminal fluid, or "with the 
filter paper used to remove them from the liquor sanguinis ; but they have not been 
detected on ova which did not undergo the cleavage of the yelk, or which had been 
immersed only in fluid separated during filtration. Whenever present in fluid in which 
ova have become impregnated, the spermatozoa have always been found in motion, 
until after they have become attached to the surface of the ovum, when their motion 
has soon ceased. In ihe Lissotritons, in the few experiments I have made on this divi- 
sion of the Amphibia, I have seen the motion continue for a long time after they have 
been in contact with ova. This leads to the supposition that a vibratile condition or 
power of motion is in some way essential to their power to effect impregnation ; not- 
withstanding that, as Wagner and Leuckardt have remarked*, no movements have 
as yet been perceived in the spermatozoa of the Isopoda and Amphipoda. If this vibra- 
tile condition be essential to their function, then the length of time which it is con- 
tinued may be of importance. 
Duration of Motive Power in Spermatozoa. — Spallanzani found that water mixed 
with but a small quantity of seminal fluid of the Frog retained the property of im- 
pregnating ova longer than pure semen^f-. When inclosed in a glass tube, the semen 
of the Toad was not impaired at the end of six hours, but was useless at the end of 
nine:J: ; while a small quantity from the Frog, mixed with water and preserved at a 
temperature of about 40° Fahr.§, was still efficient at the end of thirty-five hours. Re- 
sults obtained by myself have fallen short of this extended period, even when the in- 
fluenee of temperature has been attended to. The difference of result may to some 
extent be accounted for in the condition of the fluid, and in the way in which it has 
been obtained. Spallanzani says he obtained it both from the vesiculm seminales 
and the testes after opening the body. It is probable therefore that a large part of 
what he procured had not arrived at maturity, and instead of consisting almost en- 
tirely of active spermatozoa, as when it is obtained by compression of the body, the 
* Loc. cit., p. 503. t Dissertations, vol. ii. p. 193. I Id. p. 168. 
§ It may be well here to mention, that for the purpose of more easily comparing the observations recorded 
by Spallanzani, and Prevost and Dumas, with the results obtained by myself, I have, throughout this paper, 
reduced the data given by them to the scale of Fahrenheit, employed by myself ; the scale used by Spallan- 
zani being that of Reaumur, and by Prevost and Dumas the Centigrade. 
