THE OVUM IN THE AMPHIBIA. 
211 
the seminal fluid does not effect impregnation. Wagner and Leuckardt* have justly 
remarked, that it is almost impossible that the liquor seminis can have any action on 
ova which are expelled into water before the semen is ejected by the male, as in the 
case of frogs and fishes ; and it is worthy of note, that in the experiments now detailed 
not a single ovum was either completely or partially impregnated when immersed in 
water mixed only with the liquor seminis, obtained through filtration ; nor even when 
the ova were carefully bathed, as they passed from the body of the Frog, and before 
they had been brought into contact with water, with the filtered fluid from which the 
spermatozoa had been completely separated, as in Set N, No. 1, or even when the fluid 
still contained a very few dead and perfectly motionless spermatozoa. Yet this fluid 
can hardly be regarded as entirely without use, although it now appears to be of 
very secondary consequence. When the ova were placed in water with which only 
the liquor seminis had been mixed, the yelks became contracted exactly as is often 
the case in the unimpregnated ovum. Whatever may be the nature of this fluid, it 
does not appear to be essential to the conveyance of the structural peculiarities of 
the male parent to the offspring. These appear to be communicated by the sperma- 
tozoa alone, as not only did the ova that were impregnated by spermatozoa from the 
filter paper, as in Set N, No. 4, become segmented quickly, but the embryos pro- 
duced from them came forth with all the usual characters of tadpoles, and have 
passed, or are now passing (June 20) through their stages of growth as perfectly and 
as quickly as others which have been produced in the natural haunts of the species 
through the mutual concurrence of both sexes. Thus the liquor seminis does not 
even hasten the course of development of the young. Neither does it accelerate 
that of fecundation, either through direct imbibition or from becoming a solvent to 
the bodies of the spermatozoa ; as we have seen that segmentation of the yelk takes 
place most quickly in proportion to the number of spermatozoa, within certain limits, 
in contact with the ovum. And such also is the case in a state of nature. 
These facts appear to give that direct negative and refutation to the hypothesis of 
the immediate agency of the liquor seminis in impregnation which Wagner and 
Leuckardt'I' remark it has not hitherto met with ; and they lead to the supposition 
that one of the chief uses of the fluid is merely that of a vehicle through which the 
spermatozoa are more readily brought into contact with the ova. Possibly it may 
bear that relation to the spermatozoa in the viviparous vertebrata, in which it chiefly 
occurs, which the fluid medium into which the ova of Amphibia and Fishes are ex- 
pelled, bears to the spermatozoa in those classes. This view may derive some sup- 
port from the fact that the liquor seminis has recently been shown by chemical 
analysis to consist chiefly of a thin solution of mucus, with small quantities of chlo- 
ride of sodium and phosphates and sulphates of the alkalies 
* Cyclopaedia of Anatomy and Physiology, vol. iv. “ Semen,” part xxxiv. January 1849, p. 507. 
t Loc. cit., p. 507. t Id. 
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