August T, 1879] 



NATURE 



339 



Puss tried the door, and mewed, thinking, probably, some 

 one must be near, and after waiting two or three minutes in vain, 

 again sprang up the trellis, and renewed her attack on the bell- 

 wire, of course to be immediately admitted by the delighted 

 maid, who this time did ko/ cross the yard, nor ever again, I fear 

 sometimes to the inconvenience of visitors, if puss was waiting 

 for admission. 



Now I think Mr. Henslow will concede that no one ever 

 taught that cat how to ring the bell by pulling the mire. To 

 my mind she must have gone through the following process of 

 reasoning: — i. She noticed whenever the bell rang the door 

 opened. 2. In clambering up the trellis to the house-top she 

 accidentally moved the wire, and caused the bell to ring. This 

 probably occurred several times before she noticed it, but having 

 once done so, she repeated it, purposely, whenever she wanted 

 entrance ; I have often made her do it for the amusement of 

 friends, by turning her out from her snug nest by the fire on cold 

 or wet days. 



I have known dogs shake a door violently to attract attention 

 and be let in. A dear old spaniel of ours, at the Cape, used 

 to rattle the empty bucket if he was thirsty, and then come and 

 look in our faces. My horse will come up from his pasture to 

 the pump in the yard and whinny till some one gives him 

 water. I have known several dogs rear up and place their paws 

 on the old-fashioned "thumb-latch," and let themselves in. 

 Surely all this is "abstract reasoning"? These things are not 

 taught them, and they do not do all of them, even by imitation, 

 I don't go to the pump and whinny, if I want drink ! nor rattle 

 a bucket ! No ! they come by a process of mental reasoning, 

 and I am convinced all animals have it to a certain degree, more 

 or less. I could multiply instances by the page-full, but have 

 already taken up too much space. Among others I could confirm 

 the gnawing of water-pipes by rats to get at the water. 



Brit. Consulate, Noumea, May 30 E. L. Layard 



As a contribntion to the doubtless numerous cases in which 

 dogs have recognised the representations in paintings, I put on 

 record the following fact : — 



I have in my possession a small picture in which several dogs 

 are represented ; a small spaniel was frequently found standing 

 on a chair before the picture and barking at it, and this was 

 the only picture of which he took any notice. P. B. M. 



I 



Black Lizards 



From the interesting letters of Messrs. Giglioli and Ernst 

 it appears that lizards are found of a black colour where, accord- 

 ing to received ideas, they ought to be nearly white. How is 

 this anomaly to be explained ? 



With all due respect to those who have made this subject their 

 study for tens of years, it seems to me that they keep too exclu- 

 sively to one single proposition, which may be thus enunciated : 

 An organism is made to prey or be preyed upon. What I am 

 inclined to maintain is that an unfavourable climate is the 

 common enemy of all, an enemy that must be eluded. If an 

 animal be thrown into a climate too hot, or too cold, it will die 

 if it cannot speedily adapt itself to its altered surroundings. We 

 rce a mild case of this adaptation to environment in man himself, 

 the pale-face of temperate zones becoming soon in torrid zones 

 bronzed, and, after a few generations, black. The black dermal 

 covering is therefore clearly the one w hich is best adapted for 

 extreme heat. 



I submit then that here" we have the case of the lizards simply 

 stated. On the sandy beaches of Los Roques and Orchila, 

 covered with a very scanty vegetation the pitiless rays of the sun 

 must fall on the lizards in a most uncomfortable manner, to say 

 nothing of the heat reflected and radiated from the ground itself. 

 From the moment the islands were separated from the mainland | 

 a change would commence in the lizards to suit them to their 

 altered position, a change which has resulted in their present 

 wide divergence from the mainland type so far as colour is con- 



"?'''• , « . 'Wm. ACIiROYD 



aowerby Bndge, July 31 



Spicula in Helix 

 The spicula observed by your correspondent (Nature, vol. xx. 

 p. 316) lying underneath the albuminiparous gland in some speci- 

 mens of Helix aspersa are probably Spicula Amoris. Their cal- 



careous composition if coupled with a quadrangular outline would 

 establish the fact. Paul Henry Stokoe 



Beddington Park 



Distribution of Black Rat 



It may interest Mr. Middleton to know that in 1866, the 

 black rat was abundant on the top of the Island of Ascension ; 

 below, the "House of Hanover" held sway. I counted 

 about a dozen, lying in a manure pit, that had been killed in the 

 farm 'table?, during the previous two or three days, and was 

 told by a soldier, who did not think ;them anything out of the 

 way, that " there were plenty of them," E. L. Layard 



Noumea, May 31 



ON THE STRUCTURE OF THE STYLAS- 

 TERID^: A FAMILY OF HYDROID STONY 

 CORALS 1 



TTNTIL the late Prof. Agassiz in 1859 announced his 

 ^ discovery that the Milleporidaj were Hydroids and 

 not Anthozoans, it was confidently believed that all living 

 recent stony corals were most closely allied in their 

 essential structure to the common sea anemones of our 

 coasts. The majority of stony corals still remain under 

 the old category. The beautiful calcareous branched or 

 variously formed objects so familiar as ornaments or as 

 exhibits in museums are nearly all of them formed within 

 the bodies of animals which differ in no important 

 features from the flower-like anemones of our aquariums. 

 The sea anemones have no hard skeleton to support 

 their soft and yielding bodies ; the corals differ from them 

 in that they have such skeletons. These are, during the 

 life of the animals of which they form part, entirely 

 embedded within the soft tissues, and only become 

 exposed and appear in the familiar form when the 

 animals are dead and their flesh has been removed from 

 their bones by the action of decomposition or more speedy 

 solution by means of caustic alkalis. 



It seems difficult to explain how the popular error by 

 which corals are spoken of as structures built up by coral 

 "insects" arose. It is still perpetuated with consider- 

 able misleading detail in some schoolroom books, and it 

 is quite common to meet still with educated persons who 

 regard coral as analogous to honeycomb, and look upon 

 it as built up by the " insects " in much the same sort of 

 way. 



Very many corals are solitary or simple, being the 

 skeletons of single animals. As an example may be cited 

 the mushroom-coral, the common chimney ornament, 

 which is the largest known simple coral. This is the 

 skeleton of a single animal comparable with and closely 

 allied to a sea anemone. By far the greater number of 

 forms of corals are, however, compound ; that is to say, 

 they are the skeletons of colonies of animals, each com' 

 parable to a single mushroom coral but living united 

 together for mutual benefit and with their skeleton s fused 

 together to form a common support. Such are for 

 example the various branched Madreporas and other 

 similar forms, and the brain-corals so often brought home 

 from the tropics by sailors. 



Until Prof. Agassiz made the discovery above alluded 

 to it was supposed that all stony corals were, as above 

 described, Anthozoan. He found, however, to the 

 astonishment of naturalists, that the corals known as the 

 Milleporida: were the skeletons of animals allied not to 

 the sea anemones, but to the jelly-fish or Medusa: and 

 the common Hydra of our fresh-water ponds and ditches. 

 The Milleporida:, of which there are very many species, 

 which, however, fall within but a single genus, Millepora, 

 are either branched and form shrub-like or antlcr-like 

 masses of various sizes, or occur as irregular rounded lumps, 

 often spreading in their growth over dead corals or other 

 objects, and encrusting them. The Milleporesaredistin- 



' The Croonian Lecture, 1878. 



