2^8 



NATURE 



[August i8, 1923 



liana agilis. His assertion that the pads of Alytes 

 obstetricans are not pads because they have a different 

 appearance from those of Rana agilis is as unreason- 

 able as it would be to maintain that Alytes obstetricans 

 is not a Batrachian because it does not look hke 

 Rana agilis. 



Lastly, a few words on the question of adaptation. 

 In my lecture I avoided speaking of adaptation 

 because this term involves a hypothetical and teleo- 

 logical element : I feared that to use it might lead 

 to endless unfruitful discussion. Unfortunately, I 

 was unable to prevent this ; Mr. Cunningham dis- 

 cussed his own theory of adaptation in a way that 

 had little to do with the facts which I had cited. I 

 definitely declined to enter into this subject in my 

 reply, simply because it is not usual for the discussion 

 to wander so far from the subject of the lecture. So 

 far as the nuptial pads are concerned, may I refresh 

 Mr. Bateson's memory so far as to remind him that 

 not only my Alytes but also other Batrachians, and 

 especially the Discoglossidae (to which Alytes belongs), 

 have pads on places which never come into contact 

 with the female ? Bombinator pachypus, for example, 

 develops pads on two or three toes of the hind foot 

 (cf. Schreiber, " HerpetologiaEuropaea," 1912, p. 175). 

 Are these " in the wrong place " or " retouched " by 

 Nature ? 



I willingly admit that the traditional explanation 

 of the pads, namely, that they are produced by 

 friction with the skin of the female, may possibly be a 

 fable : for that reason I have referred to this view 

 with reserve and scepticism in my paper {1919, pp. 

 331. 339. 353)- It is true that the spread of the 

 thickening to regions of the skin which in the copu- 

 latory act do not undergo friction, is no valid ground 

 for rejecting the theory. Mr. Bateson has doubtless 

 himself observed that pressure thickenings and blisters 

 often extend beyond the original zone of irritation. 

 But it is by no means impossible, although of course 

 not proved (Kammerer, 1919, p. 340), that life in 

 water produces the pads ; if this were so we should 

 have a case of direct passive production but not of 

 active adaptation. The correctness of my observa- 

 tions and their relevance to the theory of heredity, 

 is not affected whichever of the explanations is 

 adopted. Paul Kammerer. 



Dr. Bateson, in a letter to Nature of June 2, 

 raises the very interesting point as to whether the 

 appearances alleged to be " nuptial pads " in Alytes 

 obstetricans are really such. Whatever their nature, 

 they are undoubtedly organised structures ; and if 

 they should prove not to be " nuptial pads," they 

 will have to be regarded as a new and arbitrary 

 feature which has appeared after subjection to an 

 experimentally altered environment for two or three 

 generations, and which persists for at least a few 

 generations after a return to normal conditions. In 

 other words, it would seem that Dr. Kammerer has 

 had success in an experiment which is almost 

 analogous to those ancient researches in which was 

 attempted the reproduction by hereditary means of 

 a surgically impressed modification. 



However, Dr. Kammerer has clearly stated that in 

 his opinion the only feature of the experiment which 

 in any way justifies such a view is that the excres- 

 cences in question are not dependent for their develop- 

 ment on the presence of a testis, and in this differ from 

 the nuptial pads of the better known Amphibia Anura. 



Dr. Bateson points to two details which make 

 " the appearance quite unlike that of any natural 

 Brunftschwielen " : first, that in Alytes there is a 

 " dark uniform surface . . . without the dotting 

 or stippling so obvious in true Brunftschwielen" ; 



NO. 2807, VOL. I 12] 



secondly, that their position does not correspond to 

 that of the nuptial pads in Rana agilis. 



Lataste's excellent drawings (Ann. Set. Nat. (6). 

 torn. 3, pi. II, 1876) show that a uniform blackness 

 of the outer layer of the pad is a chara< 

 feature of the Discoglossidae (to which Alytes 1 

 and distinguishes them from other Anura 1 ne 

 fully developed pads of Bu/o vulgaris are also uni- 

 formly black, and I have recently found that when 

 such full hypertrophy of the outer epithelium is 

 inhibited, as occasionally happens from obscure 

 causes, it may be induced by making the male 

 maintain a sexual embrace for a week or two. The 

 same effect may be produced in the summer condition 

 of the pad, and I have found that the hypertrophy 

 takes place even when the male maintains his tonic 

 embrace on thin air.* 



The pad of the Alytes " water-breed " also resembles 

 that of the Discoglossid Bombinator in having a 

 complete layer of black pigment in the cutis vera 

 which would further contribute to the uniform dark 

 appearance which Alytes so well and characteristically 

 shows. Photographs show another interesting point. 

 Very distinct connective-tissue papillae are developed 

 from the cutis vera in association with the epidermal 

 spines. Such papillae are but very slightly developed 

 in the Discoglossidae, though Lataste's picture of Disco- 

 glossus shows traces, whilst they are a characteristic 

 feature of the pads of many other Batrachians. 



The epidermal spines are very obvious in the intact 

 specimen, as I have repeatedly seen both with lens 

 and binocular microscope, and as many others have 

 witnessed in my presence. Of course, they are 

 practically impossible to photograph on account of 

 the glistening of a wet specimen, but a photograph 

 at least makes clear what areas of skin cire affected. 

 These include nearly the whole of the palm, the radial 

 surface of the inner metacarpal and part of the first 

 phalangeal joint of the thumb, and more or less of 

 the ventral and radial surfaces of the forearm, passing 

 over the dorso-radial margin of the inner carpal 

 tubercle. The Discoglossidae are remarkable for the 

 very various positions in which the histological 

 features of Brunftschwielen may manifest themselves, 

 on the chin, belly, thighs, toes of the feet even ; in 

 other words, they are not necessarily dependent on 

 contact with the female for their development. Dr. 

 H. Gadow has shown me his sketch of the nuptial 

 pad in Alytes cisternasii, Bosca., where it is developed 

 on the tip of the thumb, extending on the palmar 

 surface. Even in the common toad I have frequently 

 observed the nuptial rugosity extending on to the 

 palmar surface of the inner carpal tubercle. 



Questionable as it is to draw conclusions on 

 anatomical points by analogy from other animals, it 

 is even more unsafe to do so as regards their habits 

 and postures ; Alytes does not belong even to the 

 same suborder as Rana agilis. De ITsle (Ann. Sci. 

 Nat. (6), tom. 3, p. 18), in his account of the cervical 

 clasp of Alytes, says with regard to " les paumes," 

 " les applique centre le cou de la femelle." More- 

 over, although he gives no definite description of the 

 attitude of the hands during the inguinal clasp, he 

 describes how, w-ith the fingers interlaced, the two 

 backwardly directed internal digits participate in the 

 well-known chafing of the cloaca, which seems to me 

 anatomically impossible if the hands are so much 

 everted that the palms do not come in contact with 

 the pubic region, the groins, or at least the thighs of 

 the female. Michael Perkins. 



Trinity College, Cambridge, 

 June 16. 



' The surgical details of this experiment are of no importance in the 

 present connexion. 



