July 3, 19 19] 



NATURE 



345 



that the case rests. This photograph, said to be the 

 work of Prof. E. D. Congdon, of Harvard, is extra- 

 ordinarily bad. It represents a Batrachian lying on 

 its back, seen from in front. Were we not told that 

 it is Alytes, the fact could not have been ascertained, 

 for all but the hands is a blur. The hands are seen 

 from their dorsal surfaces. On the radial side of the 

 'jorisi of the right hand is a lump which Dr. Kam- 

 merer claims as a Brunftschwiele. The phalanges of 

 the thumb, as Dr. Kammeror expressly declares, are 

 unmodified in this specimen, and no Schwielen are 

 visible on the left arm or hand at all. Though on 

 analogy with other genera Schwielen might well occur 

 on the wrist or forearm, the proposition which Fig. 2 

 is intended to support is not that set forth in the 

 original paper which I criticised (c/. especially Arch. 

 Entwm. 1909, x.wiii. Taf. xvi., where a modified 

 thumb is vaguely represented). In the text of the 

 present paper we are told that the Schwielen are very 

 variable in position and extent. I do not, however, 

 find any mention of modification in digit iv. This 

 finger is, of course, external, and could scarcely func- 

 tion in the embrace ; nevertheless, the outer side of 

 digit iv. is most conspicuously thickened in the right 

 hand of the animal shown in Fig. 2. So striking is 

 this appearance that everyone to whom I have shown 

 the figure at first sight supposes this thickening to be 

 the Schwiele illustrated. I myself, on looking at the 

 picture before reading the details, had no doubt that 

 this was the Daumen with its excrescence, the hand 

 being thus supposed to present a palmar view. Dr. 

 Boulenger at once pointed out to me that this inter- 

 pretation was impossible, for the reason, among 

 others, that the comparative lengths of the digits 

 proved the hand to be shown in dorsal view, and that 

 the modified digit is iv. It must be remembered that 

 the photograph is so indistinct that much is left to 

 the imagination. 



The peculiarity of the right digit iv. would be still 

 more manifest if Fig. i, which gives a normal Alytes, 

 were a genuine photograph. It has, however, been 

 so clumsily painted up that the extremities are not 

 like those of any animal. Each finger and toe has 

 a painted outline, not always- in the right place, and 

 only on comparison with actual specimens can the 

 fulf extent of the modification in digit iv. of Fig. 2 be 

 appreciated. As it stands, this digit is very like the 

 Daumen of the original figure. I will not yet venture 

 on a positive interpretation, but I may remark that 

 what the new evidence suggests is that these modifica- 

 tions, whatever they may be, and to whatever cause 

 thev may be due, can also appear on the outside of 

 digit iv. 



I find it difficult to understand why, if these struc- 

 tures are as Dr. Kammerer declares, he did not make 

 a proper series of photomicrographs of them in situ, 

 showing their several positions and forms — no very 

 hard task for such an institution as the Versuchsam- 

 stalt. Entomologists and students of fungi make such 

 photographs constantly. Even one good ordinary photo- 

 graph or drawing would have shown more than the 

 .ambiguous pictures now offered us. If anyone wishes 

 to see how Alvtes looks in a good photograph, he 

 should turn to Boulenger {Bull. Ac. Roy. Belg.. 1912, 

 p. 573). The latest of Dr. Kammerer's figures dates 

 from 'July, 1913. A long series of Arch. Entwm. has 

 been published during the years of the war, often 

 with magnificent plates. Dr. Kammerer does not 

 state how manv modified Alytes he has had, but by 

 implication they have been numerous. If, on second 

 thoughts, he was unwilling to send one to England, 

 could he have resisted the temptation to send one to 

 the Berlin Museum to be shown to Prof. Baur, and so 

 confound him and other sceptics? Three years had 

 elapsed sinc€ we openly expressed our disbelief, but 

 NO. 2592, VOL. 103] 



I know that up to January, 1914, no such specimen 

 had been sent. 



Prof. MacBride urges that sceptics should repeat 

 experiments on the inheritance of acquired characters. 

 We, however, are likely to leave that task to those 

 who regard it as a promising line of inquir\'. Why 

 do workers in that field so rarely follow up the claims 

 of their predecessors? Each starts a* new hare. 

 Scarcely has one of their observations been repeated 

 and confirmed in such a way that we could be sure 

 of witnessing the alleged transmission if we were to 

 try for ourselves. Brown-Sdquard's observation 00 

 guinea-pigs is an exception. That has been repeated 

 by various observers, until at length, by the work of 

 Graham Brown, the mystery may be regarded as 

 I explained. The observation was true, but the inter- 

 j pretation was faulty. As I have often remarked, 

 j acquaintance with the normal course of heredity is an 

 indispensable preliminary, without which no one can 

 interpret the supposed effects of disturbance. This 

 knowledge of normal genetic physiology is being 

 slowly acquired, and already we have enough to show 

 that several variations formerly attributed to changed 

 conditions should not be so interpreted. Even in this 

 case of Alytes, were a male with incontrovertible 

 Brunftschwielen before our eyes, though confidence 

 in Dr. Kammerer's statements would be greatly 

 strengthened, the questiop of interpretation would 

 remain, pending the acquisition of a knowledge of 

 Batrachian genetics. W. Batesox. 



June 22. 



The Food of Rats. 



Ix N.ATURE of September ig, 1918 (vol. cii., d. 53) 

 a summary is given of an article by Prof. P. Chavigny 

 on the food of rats. Some of the statements in this 

 article appear to me to be extraordinary, particularly 

 the alleged necessity for rats to get cooked human 

 food. The hordes of rats which swarm along our 

 foreshores, and in granaries and like places, could not 

 possibly get sufficient cooked human food to keep 

 them alive, yet they are plump and well-fed. Any- 

 one who has kept fowls or ducks in a rat-infested 

 place knows that rats will carry off and devour chicks 

 and ducklings, even dragging them from under the 

 brooding mother, eating them raw. Attacks on living 

 and dead human beings and smaller animals are by 

 no means rare. Along the water-front rats freely 

 catch and eat crabs, and they will devour raw fish 

 with avidity. 



Certainly rats will eat cooked food when they can 

 get it, but they are omnivorous feeders, and I have 

 personally known them not merely to gnaw, but to 

 devour pumpkin, melon, apple, and other fruits. Of 

 pumpkin-seeds they are very fond, and an apple-core 

 makes a good bait for a trap. They do not seem to care 

 much for raw beef; I have noticed them attack raw- 

 potatoes and pumpkin-seeds, neglecting raw steak 

 which was lying alongside. Under a creeper in my 

 garden near Sydney the common snail (H. aspera) 

 was very abundant, and M. decumanus used to devour 

 large quantities; the apex of the shell was always 

 bitten off so that the mollusc could be readily ex- 

 tracted. On the Upper Waikato River, New Zealand, 

 the same rat dives into the water and gathers the 

 fresh-water Unio. On the river-banks the shells are 

 gnawed open and the animal eaten. The shells are 

 alwavs bitten through at the same spot of one valve, 

 but I forget now whether that was the right or left 

 one. 



In Australia at certain seasons a "cutworm " moth, 

 known as the " bogong " or " bugong " (Agrotis 

 inftisa), swarms in myriads in many places, and is, 



