so 



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 npon the 

 living animal, and by microscopic investigation, the discovery 

 of ray 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 

 herns, Coronella mistrlaca, Lacerta ci'ocea, and Anguis 

 fragilis, as well as in the oviparous Lizards, Lacerta agilis 

 and viridis, and also in the American Ameiva vulgaris, 

 Crotalus Caiesbaei, and Eplcrates 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 genuine 

 Snakes and Lizards, which I afterwards investigated, is 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 far Anatomie unci Physiologic. 



