OcTOIiKK 4, 1894] 



NA TURE 



547 



whoie heads were not ready. I prefer the former hypothesis, 

 for it is not, in this case, (the inheritance of characters casu- 

 ally acquired by a few chance individuals, but of characters 

 which have been regularly acquired by the race for several 

 generations as an active organic adaptation to the environment. 

 It is needless here to multiply illustrations, but this and 

 kindred cases have led me to ask whether too much attention 

 has not been paid to single organisms and the modifications of 

 chance individual^, whereas if a whole colony of similar organ- 

 isms invade a new region, all have to adopt new habits of life ; 

 the young members of the colony and the new young con- 

 tinually born, being plastic, will, before they are adults, show 

 marked structural modifications in adaptation to these new 

 habits. They are actively modified by these functional adapta- 

 tions to their environment. Natural Selection will winnow out 

 those who do not keep in training, and at the same time in- 

 fallibly compel the successive generations to perfect themselves 

 earlier and earlier. We should thus have stages (but without ap- 

 preciable breaks in the sequence) in this evolutionary process, (i) 

 The young are born and continue for some time like the ancestors 

 of the group, while the adults show cunsiderable structural 

 modification; (2; the new-born young resemble the ancestors 

 of the group, but commence early to show the functional adap- 

 tations of the adults ; (3) the new-born differ slightly from the 

 ancestors of the group, inheriting (or possessing •"accident- 

 ally ") slight modifications in the right direction which 

 enable them still earlier to perfect the necessary adaptation ; 

 i4) the young are born with the structures necessary to the 

 immediate adoption of the habits required by tlie environment. 



It seems to me that, in this way, we actually have the trans- 

 mission of acquired characters by inheritance, this inheritance 

 coming in as a natural term at the end of a long series of 

 individual acquirements. The prime factor in the evolution of 

 new forms is, therefore, the vital response to the environment 

 of living colonies of exquisitely sensitive organisms ; Natural 

 Selection not only perfects, but drives the resulting modifica- 

 tions back earlier and earlier in the life-history of each indi- 

 vidual of the colony tintil they arc inherited. 



This principle, it seems to me, explains the degeneration of 

 structures which are "only passively functional," such as a 

 hard shell. If the environment no longer requires a shell, it 

 will not be maintained. It is inherited, say, from ancestors, 

 but each fresh generation, or in the case of the Crustacea, each 

 moult, gives a new start. If the shell owed its origin to the 

 inorganic environment, it would cease to be developed when 

 the special stimulus to its production were withdrawn, for the 

 skin which secretes the shell is passively functional only so far 

 as the organism is concerned ; as a living tissue it is actively 

 responsive to its environment. Or again, the shell owed its 

 origin to the protection it afi'orded from enemies, and thus 

 partly to the survival of those which accidentally had slightly 

 thicker skins ; but partly, and I think chiefly, also to the 

 powers of the skin as a complex tissue to resist the attacks of 

 the many small enemies, such as animal and vegetable para- 

 sites, which are a constant element in almost all environments. 

 In this case, also, with each generation or moult we have a 

 fresh start ; on the removal of the constant irritation from these 

 enemies, the energies of the animal would be otherwise em- 

 ployed than in re-developing its shell. 



In order to account for the progressive or retrogressive 

 modifications in the sterile workers of Ilymenopterous colonies, 

 we have in the same way to assume the functional modification 

 of the plastic young as the prime factor ; Natural Selection not 

 only perfects these modifications, but drives them baik earlier 

 and earlier in the life histories of the individuals. We can thus 

 understand that a stage might be reached when the difference 

 of the food administered to the larva might modify its course of 

 development. The structural modifications of the workers in 

 this case are not inherited, but they are also not primarily due 

 10 Natural Selection, but to the response of organisms in 

 cver-reeurring plastic series to the requirements of their en- 

 vironment. 



Again, the ceaseless efforts of the young individuals of a 

 colony to adapt themselves to a new environment can alone, it 

 seems to me, account for the possible utilisation of congenital 

 variations, which are useless in themselves without concomitant 

 variations. These latter will be acquired by the efforts of the 

 organism, so far, that is, as to render the lormer functionally 

 useful.. 



On the other hand, the " time " difficulty in evolation 



admits of easy solution if it can be shown that groups of organ- 

 isms actively respond to changes of environment, as plants 

 adapt themselves to 3 new surface by the plasticity of their 

 growing shoots. Further, the difficulty that organisms are 

 known to have remained practically unchanged through immense 

 geological periods, is explained by the supposition that their 

 environment must have also remained practically unchanged. 



For the solution of many of the difficulties in evolution, we 

 have then to look to the functional response of colonies of 

 organisms, and of the living parts of such organisms to their 

 respective environments. This power of adjustment accounts 

 not only for the formation, but also for the maintenance 

 of species. The force of Heredity has been overstated, 

 while the power of immediate vital response of delicately 

 balanced organisms to every slight change in the en- 

 vironment has been very much understated. If we keep in 

 view the ever-recurring generations ol plastic young, the direct 

 stimulus of the environment is seen almost necessarily to be a 

 force of prime importance perpetually overmastering the some- 

 what exaggerated rigidity of species attributed to heredity. 

 There is no such thing as rigidity ; everything is rather in a 

 state ol flux. Is this unending variation, always in adjustment to 

 the environment, due to Natural Selection taking advantage of 

 the occasional accidental slips in an otherwise rigid heredity ? 

 or, is it due to the direct response of organisms in a state of 

 finely balanced equilibrium ? This latter seems to me the more 

 probable, the resulting structural modifications being, on the 

 one hand, hindered by Heredity ; on the other, if the con- 

 ditions require it, hastened and perfected by Natural Selection. 

 This hastening action of Natural Selection leads inevitably to 

 inheritance. 



The evolutionary theories known as Lamarckism and 

 Darwinism, only break down when they are supposed to be 

 mutually exclusive. Is it not possible to unite them somewhat 

 in the manner here suggested ? H. M. Bernard. 



Natural History Museum, September 17. 



The Great Nebula in Andromeda. 



I.M reference to Dr. A. .\. Common's review of Dr. Roberts' 

 beautiful collection of celestial photographs (Nature, No. 

 1297, September 6), where he says "There is a fair pre- 

 sumption that in course of time the rotation of the outer 

 portion (of the great Andromeda nebula) may perhaps be 

 detected by observation of the positions of the two outer de- 

 tached portions in relation to the neighbouring stars," I wish to 

 point out that changes of this kind will perhaps be detectei 

 much sooner than it is generally expected. 

 -Ill the accompanying drawing (presented May 2, 1S94, to the 

 S^'iiete Astronoiiiiijue de /■ranee), a-l/ indicates the outline of 



Ncb./j 44. 



the small elongated nebula h 44, as it was seen by Trouvelot at 

 Cambridge (>fass. ) in 1S74 ; e-d the limits of the nebulosity 



NO. I 30 1, VOL. 50] 



