30 



NA TURE 



\Nvv. 13, 1873 



to each hind foot. Passing its whole life in perpetual 

 darkness, it is blind and colourless, except the external 

 gills, which are red. This animal retains during the 

 whole of life not only the gdl aperture on each side, but 

 also the external plumose gills which are transitory in the 

 Anoura and in all the Urodela hitherto mentioned. Here 

 then we first meet with an animal which may be said to 

 be a permanent and persistent Tadpole, yet rather like an 

 Eft-tadpole than like that of the Frog. 



A North American Urodele, misnamed (for it is silent 

 enough) Siren, also presents us with permanent external 

 gills, and it offers another interesting resemblance to the 

 tadpole of the frog in that it is furnished throughout life 

 with a horny beak. It has also another remarkable cha- 

 racter in which it stands alone in its class. Hitherto 

 every rel itive of the frog has had, like it, four limbs in the 

 adult condition. In the Siren, however, we for the first 

 time make acquaintance with a creature belonging to the 

 class (though not to the order) of frogs and toads, which 

 is devoid altogether of hinder (or p:lvic) limbs, being in 

 this respect like the whales and porcupines amongst 

 beasts, and like the little lizard, Chirotcs, amongst 

 reptiles. 



Another North American Urodele, Mcnobranchus, pos- 

 sesses throughout the whole of life both gill openings 

 and external gills. But it is furnished with four limbs, 

 and in other respects more or less resembles in appearance, 

 as it does in size, the genus Mciiopoina before noticed. 



Finally there is a genus of this order {Urodela) which 

 has of late presented circumstances of peculiar interest. 

 This is the Axolotl of Mexico, which was long considered 

 by Cuvier to be a large Eft-tadpole, possessing as it does 

 permanent gills and giU-openings, with some other cha- 

 racters common to the Eft-tadpole stage of existence. 

 At length, however, its mature condition was considered 

 to be established by the discovery that it possesses perfect 

 powers of reproducing its kind. 



For some years, individuals of this species have been 

 preserved in the Jardin des Plantes at Paris, and a few 

 years ago one individual amongst others there kept was 

 observed, to the astonishment of its guardian, to have 

 transformed itself into a creature of quite another g< nus — 

 the genus Ambly stoma, one rich in American species. 

 Since then several other species have transformed thpin- 

 selves, but without affoidmg any clue as to the conditions 

 which determine this change — a change remarkable in- 

 deed, resulting as it does not merely m the loss of gills 

 and the closing up of the gill-openings, but in remarkable 

 changes with respect to the skull, the dentition, and other 

 important structures. 



There is, moreover, another and very singular fact con- 

 nected with this transformation. It is that no one of the 

 individuals transformed (although we must suppose that 

 by such transformation it has attained its highest deve- 

 lopment and perfection) has ever yet reproduced its kind, 

 and this in spite of every effort made to promote repro- 

 duction by experiments as to diet and as to putting to- 

 gether males and females both transformed, also 

 transformed males with females untransforraed, and males 

 untransformed with females transformed. Indeed, lire 

 sexual organs seem even to become atrophied in these 

 transformed individuals. Moreover, all this time the 

 untransformed individuals have gone on bringing forth 

 young with the utmost fecundity, no care or trouble on 

 the part of their guardians being required to effect it. 



A fact more notewortny could hardly be imagined in 

 support of the view of specific genesis put forward 

 recently.* Heie we have a rapid and extreme transior- 

 mation taking place according to an unknown internal 

 law of the species which transforms itself. No one, 

 moreover, has been able to detect the conditions which 

 determine such transformation (though it takes place 

 under the eyes, and in the midst of the experiments of 



* See Genesis of Species, chap, xi. 



its observers). This latter fact affords abundant evidence 

 how obscure and recondite may be the conditions which 

 determine the transformations of specific genesis, and 

 how utterly futile are observations as to an apparent homo- 

 geneity of readily appreciable conditions. They are so 

 since it seems to be just such recondite ones which really 

 determine the changes just referred to, and probably, 

 therefore, other changes analogous to them. 



It may be a question whether the genus Mcnobranchus 

 may not also be a persistent larval * form, and one which 

 now never attains its once adult form. If so, it is most 

 probable that its lost state was similar to that of the ex- 

 clusively American genus Spclcrpes, the larva of which 

 Menobranchiis much resembles. With respect to Proteus 

 and Siren no conjecture of the kind can yet be made. 



Individuals belonging to the common English species 

 ( Triton cristatus) occasionally retain some of the external 

 characters of immaturity, in spite of having attained re- 

 productive capability ; and a European species [Triton 

 alpertris) often matures the generative elements while still, 

 as to external appearance, more or less in its tadpole stage 

 of existence. The adult condition, however, is normally 

 and generally at ained by it. 



The geographical distribution of the Urodela is very 

 remarkable. North America is the head-quarters of the 

 order, and, with rare and trifling exceptions, the whole 

 are confined to the Northern hemisphere. The exceptions 

 are certain forms which extend down the Andes into 

 South America, and one or two species of Amblystoma, 

 which similarly descend along the highlands of South 

 Eastern Asia. Urodeles are absolutely wanting in 

 Hindostan, Africa south of the Sahara, the Indian Archi- 

 pelago, Australia, and New Zealand. As might be ex- 

 pected, that part of Asia which is nearest to North 

 America, namely China and Japan, is the region of the 

 old world most richly peopled by species of Urodela. Al- 

 together the world's surface may be divided according to 

 its Urodele population into three regions. The first will 

 comprise Europe, Africa north of the Sahara, and North 

 Western Asia. The second will include Japan and 

 Eastern Asia. The third will be formed by North 

 America, with a slight extension southwards into South 

 America — a division which by no means coincides with 

 that indicated by the Anoura. 



The above two orders {Anoura and Urodela) comprise 

 all the animals most nearly allied to the common frog, of 

 all those outside its own order. There is, however, 

 another small ordinal group of animals which remains to 

 be here noted, because of all existing creatures they come 

 nearest to the frog, after the Urodela. 

 (To be continued^ 



INAUGURATION OF THE LINNEAN SO- 

 CIETY'S NEW ROOMS 



Opening Address by the President 

 T T is now seventeen -years since the Government first 

 -*■ recognised the claims of our Society to encourage- 

 ment and assistance on the part of the State, as one which 

 devoted itself to scientific pursuits unremunerative to its 

 members, but tending directly or indirectly to public 

 benefit ; and since then a sense of the justness of such 

 claims on the part of pure natural science has become 

 gradually more general. We are no longer in the days 

 when a Peter Pindar could turn the Royal Society and its 

 president into ridicule as boiling fleas to ascertain 

 whether they turned red like lobsters. The Times, in- 

 stead of a short leader dismissing the British Association 

 meetings in a similar strain of bamer, devotes daily, 

 during the lime of its session, half a dozen columns to the 

 details of its proceedings. And our own department in 

 natural science is now admitted to be one of the most im- 



* The young of the Frog or Eft is called a larva. 



