5 
minutely the intermaxillary bone of the nearly developed 
embryo. Nevertheless it was not new. Already in the year 
1841, J. Muller, as I heard afterwards from himself, had dis- 
covered it in alcoholic specimens of the fully developed embryos 
of snakes and lizards,* and I am glad of confirming upon the 
living animal, and by microscopic investigation, the discovery 
of my highly esteemed teacher and friend. 
I found afterwards the same tooth, (which we may call 
egg-tooth from its only function) in the embryos of all 
German Snakes and Lizards, in the viviparous Vipera 
berus, Coronella austriaca, Lacerta crocea, and Anguis 
Jragilis, as well as in the oviparous Lizards, Lacerta agilis 
and viridis, and also in the American Ameiva vulgaris, 
Crotalus Catesbaei, and Epicrates cenchris ; of which the 
two latter are also viviparous, and do not have the thick leathery 
shell which is found in all oviparous Snakes and Lizards. In 
the Crocodile, of which I investigated fine specimens, just 
hatching, in the Zoological Museum in Berlin, I could not find 
any trace of this tooth. This fact, stated already by J. Muller, 
shows again, with many others, that Crocodiles must be separ- 
ated as a distinct order of reptiles from the genuine Lizards, 
and that the latter are nearer to the Snakes than to the Croco- 
diles. The eggshell of a Crocodile is like that of a Bird or 
Turtle, hard and very rich in lime, thus easier to be broken by 
the hard snout of the young, as with Birds and Turtles, by the 
horny wart on their bills; while the eggshell of the genuino 
Snakes and Lizards, which I afterwards investigated, 1s com- 
posed of several layers of very fine but strong fibres, felted 
together in a leathery elastic membrane (Fig. 6.) The time 
and manner of the formation of these fibres is not clear; some 
observations, however, made in the same summer, upon fresh 
eggs, seemed to me to show that they originate from cells. I 
saw in the felt, here and there, yellowish, oval bodies, gener- 
ally provided with a small nucleus. I succeeded in separating 
some, and saw these yellowish bodies, clearly continued 
on one side into very long fibres. Thus these bodies seem to 
be the cells from which the fibres grow. Now these cells 
at the ends of the fibres were of different size, some being 
four times as large as the diameter of their fibres, and others 
not much thicker than the fibre itself. I suppose that this 
latter state was the end of the evolution of the cell, and so we 
understand why, at a later time, when the eggshell is fully 
grown, we no longer find these cells. (Some of these fibre cells 
or bulbs are shown in fig. 7.) 
* See J. Muller, Archiv fur Anatomie und Physiologie. 
