EARLY ONTOGENETIC PHENOMENA IN MAMMALS. 273 
Amniota. 
Amnion. 
Allantois as respiratory organ. 
Umbilical reside or yolk-sac pos- 
terior to and qnite separate from 
liver. 
No true blastopore. If any open- 
ing occurs to which this term 
has been applied it never occurs 
until after the first formation 
of the future gut cavity, i . e . it 
is a neurenteric canal. 
Spiiticle always present and open 
as long as any other cleft. 
Peculiar epidermic skeleton of ho- 
mologous parts (scales, feathers, 
hairs). 
Vertebral column gastrocentrous 
form of Arcocentrous tyjDe. 
Ribs well developed and reaching 
sternum (except speciahsed 
types, e.g. Chelonia, Ophidia). 
Hypoglossal comes off within the 
skuU. 
Neck. 
Metanephros in connection with 
a special outgi’owth from the 
mesonephric duct to form the 
ureter. 
Mesonephric duct never conveys 
urine in adult. 
Pronephros of embryo rudimen- 
No amnion. 
No respiratory allantois. 
Yolk-sac either anterior or in con- 
nection with liver. 
Blastopore ; always correlated 
with the fii’st formation of the 
gut cavity. 
(Gyninophiona may be inter- 
mediate.) 
Spiracle often rudimentary or 
absent. 
Nothing comparable. 
V ertebral column notocentrous 
and pseudocentrous forms of 
Arcocentrous type. 
No ribs, or if present they do not 
reach the sternum. 
Hypoglossal always outside the 
skull. 
No neck. 
No metanephros nor special out- 
growth from the mesonephric 
duct. 
Mesonephric duct itself is ureter. 
Pronephros of embryo weU de- 
veloped. 
taiy. 
The only other point to which I wnll allude is Hubrecht’s 
question, “ Whether many of our Dipnoi, Ganoids, and 
Teleosts may not have had terrestrial ancestors,’’ p. 153. 
Naturally, I feel proud that I should have been bold 
enough to make a similar suggestion for the Teleosteaus in 
which are probably of prime importance (though some of 
these are already given in other authors’ lists, e.g. Gadow, H., 
‘ Zeits. f. Morph, u. Phys.,’ Bd. 4). 
Anamnia. 
