3^ Hybridisation of Amphibians , &c. [January, 
disputed, it follows that the germs of mature ova may 
increase for successive generations without fecundation. 
The residual germs cannot therefore be at once set down as 
doomed to perish. These germs which escape fecundation 
would explain the “ reversion ” of hybrids, if indeed it exists 
in a pure state. But a pure reversion would be intelligible 
even without such superfluous germs, as in hybridisation 
fecundation often fails, so that in one and the same ovum, 
along with united germs, there may co-exist unpaired male 
and female germs. 
As to the cause of the paradoxical behaviour of the eggs 
of R. arvalis, fecundated with the sperm of R. fusca, Prof. 
Pfluger refers this phenomenon to “ fractionated fertilisa- 
tion.” According to the observations of M. Fol the spermato- 
zoon is immediately attacked by the yolk of the ovum at the 
moment of contact ; consequently also when only the point 
of the head touches the yolk, the thicker part being kept 
back by the narrowness of the micropyle, or by the excessive 
stiffness of the gelatinous matter. 
We may thus imagine that the point of the head of a 
spermatozoon which has penetrated into the yolk, whilst the 
thicker portion is wedged fast, may be resolved into particles, 
thus producing an abnormal segmentation. 
This explanation of anomalous hybrid segmentation by 
“ fractionated fecundation ” renders it intelligible why in 
hybrid fertilisation we can find no rules. Each egg becomes 
differently segmented, perhaps because the quantity of the 
spermatic substance differs in every case. Such anomalous 
segmentation is not inseparably connected with hybridism ; 
it occurs also during the fecundation of the ova of Bombi- 
nator igneus with the normal sperm of its own species, if too 
little water is present. The gelatinous mass enveloping the 
ovum remains then very stiff, and it is possible that the 
spermatozoa may often fail to penetrate into the yolk. If 
the fact that the hybridisation of nearly related Batrachian 
forms leads sometimes to normal and at other times to the 
most abnormal developments may be explained as above, it 
is very probable that both irregular segmentation and en- 
tirely negative results in crossing the Anoura are due merely 
to such secondary complications. The true law is probably 
reciprocal fertility in all with normal segmentation, and, with 
few exceptions, death during the first stages of development. 
Whether this law extends to the hybridisation of the Anoura 
and the Urodela cannot be asserted —Pjtiigcr's Archiv. und 
N aturforscher . 
