THE EVIDENCE FROM DEVELOPMENT. 243 



morphosis, that her experiments were begun on June 12, 1874, 

 with five larvae, about eight days old. At the end of June the front 

 legs had appeared in the healthiest specimens, and on July 9 the 

 hind limbs were developed. Towards the close of November, one of 

 these larvae appeared to remain constantly at the surface of the 

 water, and from this sign Fraulein von Chauvin concluded that the 

 proper and natural period had arrived for the assumption of the 

 Amblystoma-form. This specimen was accordingly placed, on 

 December i, in a vessel in which its existence was divided between 

 a water life and a terrestrial one. The water being gradually 

 diminished, the gills began to shrivel, and on December 4 the 

 animal left the water, and remained on the earth and moss in the 

 vessel. At this period, it moulted its skin for the first time. Then, 

 also, between December i and 4, the dorsal crest, or fin, shrivelled 

 in addition to the gills, and the tail became rounded like that of 

 the Amblystoma. The original greyish-brown colour likewise 

 changed to black, and the spots of the Amblystoma became apparent. 

 The gill- clefts were open on December 4, when the animal left 

 the water ; but in about eight days these slits were entirely closed. 

 In the other specimens experimented upon by Fraulein von Chauvin, 

 the period occupied in the metamorphosis varied somewhat, the 

 greatest differences being due, apparently, to the nutrition of these 

 forms being less active than in those specimens in which the trans- 

 formation was speedily accomplished. The general conclusion 

 arrived at from these experiments is that " Axolotl larvae generally, 

 but not always, complete their metamorphosis if, in the first place, 

 they emerge sound from the egg and are properly fed ; and if, in the 

 next place, they are submitted to the necessary treatment for chang- 

 ing aquatic into aerial respiration. It is obvious that this treatment 

 must be applied very gradually, and in such a manner as not to 

 overtax the vital energy of the amphibian." Weismann concludes 

 that " most Axolotl larvae change into the Amblystoma-form when, 

 at the age of six to nine months, they are placed in such shallow water 

 that they are compelled to respire chiefly^by their lungs." 



The Axolotl does not, so far as is known, become converted into 

 the Amblystoma-form in its native region. In the Mexican lakes it 

 appears to be perpetually and only known as the gilled Axolotl. 

 Professor Cope also states that these Mexican animals, when bred in 

 captivity in America, reproduce their like, and do not show any 

 tendency towards transformation. Yet in France and elsewhere, as 

 already remarked, the Axolotl becomes transformed into the Ambly- 

 stoma in its domesticated or captive condition ; but it is necessary 

 to remark that the exact species which became metamorphosed in 

 France was either the Siredon lichenoides of Baird, or some allied 

 form, and not the Siredon Mexicanus of Mexico. Baird states that 



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