290 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA. 
on the simple application to the egg of the diffluent spermatic substance. In the 
absence, then, of all proof that simple fusion only of the substance of the spermato- 
zoon with the contents of the egg is the chief condition of fecundation, we ha\ e, in 
the facts now referred to, much reason to regard fecundation as primarily dependent 
on the existence of a force or power in the spermatozoon, by which this body is 
enabled to arrive at the object to be fertilized, and which, visibly expressed in that 
of its power of motion, is lost quickly after it has penetrated into the yelk-membrane 
or yelk -.—this, probably, is the instant of fecundation. May not the spermatozoon, 
then, be viewed as the organ of a special form of force in the male body for the pro- 
duction of these results, in the same way as the nervous structure is regarded as 
that of the nervous, and the muscular as that of muscular power? We have already 
seen that its function is exercised more or less readily and perfectly in relation to 
two conditions ; first, that of its full maturity, in which its power of motion is most 
intense ; and next, in relation to the influence of external physical agencies, which 
cause this power to be evolved through its organic composition, in a greater or less 
degree, whether the external influence be that of heat, or the operation of a chemical 
power, as in the instance of potass in the preceding experiments. 
