Embryonic Development of the Crocodile. GO 



Tlie fact that sounds are produced bj the young in the qq^ 

 was unknown to anybody here. The natives Laughed at me 

 wlicn I spoke about it, until by listening they were convinced 

 of their mistake. The sounds are produced with the mouth 

 closed, apparently by powerful contraction of the ventral 

 muscles, much as we make a noise when hiccoughing. The 

 sound, too, is similar. 



When the young animals have emerged the old crocodile 

 goes with them to the water. My taxidermist, a thoroughly 

 trustworthy man, who has previously travelled with Dr. 

 Fischer, told me that a short time before he had seen a large 

 crocodile with a tribe of about twenty young ones travelling 

 over a stretch of sand to the water. He stated that the old 

 one was remarkably savage. That the just-hatched young 

 are able, without help from the mother, to break through the 

 superincumbent layer of sand I believe that I am entitled, 

 according to the experiments which I have made, to deny as 

 emphatically as possible. Of the eggs which were covered 

 with a layer of sand about 1^ to 2 feet in depth it is true that 

 a few showed feeble attempts on the part of the young to 

 escape, in that the shell was broken at one point, while some- 

 times the young animals had protruded the tip of the snout ; 

 but they had invariably perished, probably from want of air. 

 The eggs which were only lightly covered with sand pre- 

 sented no difficulties to the young in escaping. 



The process of hatching is preceded by a change in the 

 position of the embryo, with partial destruction of the embry- 

 onic membranes, so that the tip of the snout of the young 

 animal now comes into contact with one end of the egg ; at 

 any rate this was the position of all embryos which were 

 ready to emerge. The piercing of the egg-shell is effected by 

 the mechanical operation of the egg-tooth, which is also found 

 in young birds. The rudiments of this tooth may be detected 

 at a very early stage, at the period at which the young croco- 

 diles begin to assume their definite shape, therefore when the 

 embryos are about one and a half to two months old. In the 

 just-hatched young it appears as a tooth about ^ to | millim. 

 in length, terminating in two points ; the movements of the 

 animal cause it to act precisely like a gimlet. In crocodiles 

 a fortnight old it was still distinctly recognizable. On the 

 perforation of the egg the embryonic fluid escapes and pro- 

 duces a softening of the adjacent parts of the shell, and the 

 young animal forces itself backwards through the narrow 

 cleft. A specimen which was watched from the moment it 

 pierced the egg-shell took about two hours to completely 

 emerge. As the animal forces itself through the narrow hole 



