Nov. II, 1886] 



NA TURE 



4f 



digits on tlie left side, while the two sets are continuous on the 

 liyht paw, as in Prof. Meldola's kitten. 



All the observations recorded in this paper were made in 

 Oxford. The abnormality has now been observed through nine 

 generations, and I have recorded notes of ten families, so that 

 now there is sufficient material to present in a tabular form. 



The notes given in this paper are much more complete than 

 before, because the families were born in my own house or in 

 that of a friend living near, who kindly gave me every oppor- 

 tunity of making notes. The results, however, would have been 

 far more extensive if I had received intelligence of the birth of 

 families in various quarters to which kittens had been sent. 



I believe there is little doubt that the next period of three 

 years will produce much better results in this way, for at the 

 recent meeting of the British Association at Birmingham I 

 exhibited the cats, and was able to give away three abnormal 

 females to scientific gentlemen (Prof. Haddon, Prof. Meldola, 

 and Mr. W. White) who I am sure will assist me by sending 

 complete accounts of all the families born. I remarked in my 

 last paper on the immense strength of heredity which was shown 

 in the oliservations then recoded, remembering that the results 

 were in all cases due to the mothers of the families. The con- 

 tinued observations now published serve to illustrate the same 

 facts. As 1 said before, "it is practically certain that the 

 f.\thers of the families have always been normal." There has, 

 indeed, been an abnormal male cat in Oxford for the last two 

 years — one of my kittens which I gave to Prof Moseley for a 

 museum specimen, and which has been kept in order that it may 

 be quite mature. But this cat lives at some distance from my 

 house and that of the friend to whom I gave the female kitten 

 in 1S85, and it has never been seen in our neighbourhood, while 

 numbers of normal cats have been seen in company with our 

 abnormal females. But nevertheless a family containing ab- 

 normal kittens was born in a house near that in which Prof 

 Moseley 's cat is being kept, and of which, of course, the latter 

 must be the male parent. Unfortunately, as in so many other 

 cases, I was unable to obtain any data, and the kittens are, I 

 believe, all dead. 



We therefore see in these observations a proof of the extra- 

 ordinary ease with which a distinct breed can be produced from 

 a spontaneously appearing variety. In spite of all the swamping 

 effect of continual and uninterrupted crossing with the normal 

 form, I have never been able to record a normal family, while in 

 many cases some of the kittens were equal to, or even beyond, 

 the abnormal parent in her peculiarity. This being the case, it 

 is clear that a breed would have been quickly established if 

 abnormal males had been selected to pair with the abnormal 

 females. These observations have, therefore, an interesting 

 bearing upon the existence of such a local breed as the tailless 

 Manx cats, as Prof. E. Kay Lankester pointed out to me when 

 talking over the subject. Prof. Lankester supposes that a tail- 

 less individual appeared spontaneously, and that it was con- 

 sidered interesting and a curiosity ; and when the abnormality 

 re-appeared in some of the oft"-pring, these were kept in preference 

 to the normal forms. It seems quite certain that the result might 

 have been produced in this way, and I have arranged with Dr. 

 Grabham, of Madeira, that some of my abnormal kittens shall be 

 sent to him to turn loose upon some neighbouring Atlantic rock 

 on which rabbits are the only other living mammals. I should 

 add that Prof. Lankester found a support for the theory of the 

 origin of the Manx breed of cats in the fact that there are 

 tailless breeds of other animals which are also fashionable in 

 the locality, and which seem to point to the existence of the same 

 peculiarities of taste working upon a spontaneous variety. In 

 fact, as Prof. Lankester suggested, the people may have rather 

 looked out for other tailless or abnor. rally short-tailed anim.ils, 

 when their interest had been excited by the existence of one such 

 breed. But the observations here recorded have also a bearing 

 upon thosi cases in which natural, instead of artificial, selec- 

 tion has been the agent. Granting, as I believe we must 

 do, that some adaptive characters of great importance owe 

 their beginning to flashes of structural or functional origin- 

 ality — appearing suddenly and spontaneously in one individual, 

 as the extra digits appeared in the ancestor of my cats, — 

 we see from these observations that in spite of all the effects of 

 constant intercrossing with normal forms, there would be a 

 most persistent offer of material upon which natural selection 

 might work, for the variation would appear to a greater or less 

 extent in a very large proportion of the individuals of the various 

 families produced, while again and again the peculiarity would 



be inherited in a form equal to or even beyond that of the parent. 

 It is therefore of interest to actually test a few instances in as 

 complete a manner as possible, taking care that only one parent 

 possesses the abnormality, for this is what must have happened 

 for the first few generations of any such variety which originally 

 appeared in a single individual in a natural state. It is chiefly 

 with the object of adding another to the instances already known 

 and worked out that these observations have been undertaken, 

 and will be continued and rendered as complete as iiossible. It 

 need scarcely be pointed out that such instances differ essentially 

 from all the cases in which breeds of domestic animals have been 

 established, for in these well-known and numerous breeds 

 heredity has had undisturbed possession of the field, without any 

 confliction between the normal and abnormal forms, except indeed 

 in the case of the first family produced by the original parent of 

 certain breeds of which the peculiarity appeared spontaneously 

 in a single individual, as in the breed of " otter " sheep. 



Edward B. Poulto."^ 



LIGHTHOUSE ILLUMINANTS^ 



'X'HE details of the construction of the three towers and 

 lanterns, and of the lenses and lamps in each lantern, of 

 the magneto-electric machines, and of the gas-works, have no 

 doubt been placed on record, and will be reported by the Trinity 

 House engineers. But the following may serve as a general 

 description of the arrangements. 



Three low towers, constructed of massive timber, have been 

 erected in a line inland from the higher of the two permanent 

 lighthouses on the South Foreland, the nearest being 245 feet 

 distant from the lighthouse, and the three being separated one 

 from another by intervals of iSo feet. Their height, varying 

 with the level of the ground, so that the lanterns may be on the 

 same level, is from 20 to 30 feet ; upon these structures rest 

 three similar lanterns about 20 feet in height and 14 feet across. 

 Within the lanterns are columns of lenses forming two opposite 

 sides of a hexagonal framework which rises from the base to near 

 the top of each lantern. The whole framework can be made to 

 revolve so that either column of lenses may be made to face in 

 any direction ; each column consists of three or four similar 

 lenses superposed, but the lenses forming different columns are 

 different in their purpose and structure, and in their size. One 

 column in each lantern consists of lenses designed to gather the 

 divergent rays which fall upon them from the central source of 

 light into a level sheet which spreads over the surface of sea or 

 land, but not downwards or upwards ; each of these lenses is a 

 segment of a cylinder, and may be described as a cylindrical 

 lens. The opposite column in the gas and oil lanterns consists 

 of lenses designed to gather the divergent rays, not into a sheet, 

 but into a single cluster or cone of small vertical angle, which is 

 sent forth horizontally in any one direction. These lenses are 

 made up of a central circular lens, surrounded by annular prisms 

 and segments of such prisms, the whole fitting into a rectangular 

 frame ; they may be called annular lenses. The correspond- 

 ing column of lenses used with the electric light consists of 

 cylindrical lenses with condensing prisms placed in front of them ; 

 the cylindrical lens flattens a broad cone of light into a fan, the 

 condensing prisms close the fan. 



The size of the cylindrical lenses placed in front of the gas and 

 oil lamps is the same, but the lenses in front of the superposed 

 electric lights are smaller. The annular lenses, of which three 

 form a column in the oil Lantern, are each 6 feet 3 inches in 

 height, while the four superposed annular lenses in the gas lantern 

 are each 3 feet 9 inches in height. Both sets of annular lenses 

 have the same width, namely, 3 feet 5 inches. 



The electric lights are large arc lights, supplied with the 

 electric current by three magneto-electric machines, which are 

 worked by the steam-engine in the engine-house built for the 

 ordinary work of the station. The electrical apparatus is of the 

 construction of Baron de Meritens. 



The gas-burners tried hitherto are of Mr. Wigham's con- 

 struction, consisting each of a multitude of small fish-tail jets on 

 brass stems about 6 inches long and an inch one from another, 

 arranged on the same level in concentric rings. A tall funnel, a 

 few inches above the cluster of burners, draws their flames to- 

 gether into the form of a bell. The number of concentric rings 

 may be changed quickly so as to increase or reduce the size of 



* Preliminary Report of Mr.Vernjn Harcourt to the Board of Trade on 

 the Experimental Lights exhibited at the South Foreland. 



