428 



NATURE 



{Feb. 28, 1889 



lands, are at all times to be found floating about on the surface 

 of the sea, and these, being cast up on the newly-formed islet, 

 produce, by their disintegration, the clayey materials for the 

 formation of a soil — the red earth of coral islands. Just within 

 the shore platform these pumice fragments are found in a fresh 

 condition, but as the lagoon is approached they disappear, the 

 soil becomes deeper, and the most luxuriant vegetation and 

 largest trees are found close to the edge of the inner waters. 

 The land is seldom continuous around the atoll ; it occurs 

 usually in patches. The water passes over the shallow spaces 

 between the islets and through the deeper lagoon entrances, 

 these last being kept open by the strong sand-bearing currents 

 which pass at each tide. 



The few species of plants and animals which inhabit these 

 coral islands have been drifted to the new island like the pumice, 

 or carried, many of them maybe, by birds; lastly, savage and 

 civilized man finds there a home. 



There is no essential difference l^etween the reefs forming 

 fringing and barrier reefs, and those which are known as alolls. 

 In the former case, the corals have commenced to grow close to 

 the shore, and as they grow outward, a small boat-passage, and 

 then a ship-channel, is carved out between the reef and the 

 shore by tidal scour and the solvent action of the water on the 

 dead parts of the reef : thus, the fringing reef may be converted 

 into a barrier reef; or the barrier may be formed directly by the 

 upward growth of the corals at some distance from the shore. 

 In some instances the corals find a suitable foundation on the 

 banks that surround islands and front continental lands, it may 

 be, at a great distance from the coast, and when they reach the 

 surface they form a distant barrier, which proceeds seawards, 

 ultimately on a talus made up of materials torn from its seaward 

 face. 



If the foregoing considerations be just and tenable, then it 

 would appear that all the characteristic features of coral reefs 

 can be produced, alike in stationary areas or in areas of slow 

 elevation .and subsidence, by processes continually at work in 

 the ocean at the present time. Slow elevation or subsidence 

 would only modify in a minor way a typical coral atoll or barrier 

 reef, but subsidence in past times cannot be regarded as the 

 cause of the leading characteristics of coral reefs. There are 

 abundant evidences of elevation in coral-reef regions in recent 

 times, but no direct evidence of subsidence. If it has been 

 shown that atoll and barrier reefs can be formed without sub- 

 sidence, then it is most unlikely that their presence in any way 

 indicates regions of the earth's surface where there have been 

 wide, general, and slow depressions. 



According to Mr. Darwin's theory, which has been almost 

 universally accepted during the past half-century, the corals 

 commence to grow close to the shore of an island or continent : 

 as the land slowly sinks, the corals meanwhile grow upwards to 

 the surface of the sea, and a water space— the lagoon channel — 

 is formed between the shore of the island and the encircling 

 reef, the fringing being thus converted into a barrier reef. 

 Eventually, the central island sinks altogether from sight, and 

 the barrier reef is converted into an atoll, the lagoon marking 

 the place where the volcanic or other land once existed. En- 

 circling reefs and atolls are represented as becoming smaller and 

 smaller as the sinking goes on, and the final stage of the atoll is 

 a small coral islet, less than two miles in diameter, with the lagoon 

 filled up and covered with deposits of sea-salts and guano. 



It is at once evident that the views now advocated are in 

 almost .ill respects the reverse of those demanded by Mr. 

 Darwin's theory. 



The recent deep-sea investigations do not appear in any way 

 to support the view that large or small islands once filled the 

 spaces now occupied by the lagoon waters, and that the reefs 

 show approximately the position of the shores of a subsided 

 island. The structure of the upraised coral islands, so far as 

 yet examined, appears to lend no support to the Darwinian 

 theory of formation. When we remember that the great grow- 

 ing surface of existing reefs is the seaward face from the sea 

 surface down to 20 or 40 fathoms, that large quantities of 

 coral debris must be annually removed from lagoons in suspen- 

 sion and solution, that reefs expand laterally and remain always 

 but a few hundred yards in width, that the lagoons of finished 

 atolls are deepest in the centre, and are relatively shallow com- 

 pared with the depth of the outer reefs, then it seems impossible, 

 with our present knowledge, to admit that atolls or barrier reefs 

 have ever been developed after the manner indicated by Mr. 

 Darwin' simple and beautiful theory of coral reefe. 



DARWIN VERSUS LAM ARC K> 

 A FTER a brief sketch of the life of Lamarck (1744-1829), 

 •^^ his theory was stated in his own words as follows : — 



"(i) In every animal which has not arrived at maturity, the 

 increased and continued employment of any organ strengthens 

 that organ gradually, develops it, enlarges it, and gives it a 

 power proportional to the duration of its employment : on the 

 other hand, the continued disuse of any organ gradually weakens 

 it, deteriorates it, progressively diminishes its faculties, and 

 finally causes it to disappear. 



"(2) Every feature which, under natural conditions, indivi- 

 duals have gained or lost by the action of circumstances to 

 which their race has been for some time exposed — as, for in- 

 stance, the results of excessive use or disuse of an organ — is 

 preserved in reproduction and transmitted to the offspring, 

 provided that the acquired changes were present in both 

 parents." 



The small changes thus produced and transmitted from gener- 

 ation to generation are increased in successive generations by 

 the action of the same causes which originated them, and thus 

 in long periods of time the form and structure of the descend- 

 ants of an ancestral organism may be completely changed as 

 compared with the form and structure of the ancestor. 



Given sufficient time, these small changes can have produced 

 man and the higher animals from simple primitive protoplasmic 

 animalcules. 



Prof Lankester then pointed out the truth of the first law of 

 Lamarck, but mentioned the preliminary objections to Lamarck's 

 theory, which had prevented its acceptance by the naturalists 

 of the first half of this century. He then briefly epitomized 

 Darwin's theory as follows : — 



(i) All plants and animals produce offspring which resemble 

 their parents on the whole (heredity) ; these offspring, however, 

 exhibit also new and individual features differing from those of 

 their parents (congenital variations). 



(2) In Nature there is a severe struggle for existence. Only 

 one pair out of the many thousands often produced by a pair 

 of plants or animals survive to maturity, and in their turn 

 produce offspring. 



(3) The survivors are those whose congenital variations have 

 enabled them to gain advantage over their fellows. 



(4) The surviving forms may be almost exactly like their 

 parents, but often a departure from the parental form must be 

 an advantage, however small. Such departure, or variation, 

 when IN-BORN or congenital, not only enables its possessor 

 to survive and produce offspring, but is handed on by heredity 

 to that offspring. 



(5) A successful congenital variation is intensified in the new 

 generation bred from parents in both of which it had congenitally 

 appeared. 



(6) By this process of natural selection of advantageous con- 

 genital variations, operating in countless millions of successive 

 generations, the transformation of simple into more elaborate 

 forms of life has been effected. 



The real difference between Lamarck's and Darwin's theories 

 was then explained. Congenital variation is an admitted and 

 demonstrable fact ; transmission of congenital variations is also 

 an admitted and demonstrable fact. Change of structure ac- 

 quired during life — as stated by Lamarck — is also a fact, though 

 very limited. But the transmission of these latter changes to 

 offspring is not proved experimentally ; all experiment 

 tends to prove that they cannot be transmitted. Semper's book 

 on this subject was cited as a failure in the attempt to prove 

 such transmission. 



The causes of congenital variations were next discussed, and 

 the "stirring up" of the germ-plasma by the process of 

 fertilization was pointed to as the chief 



Very minute congenital variations can be useful, and, there- 

 fore, selected ; but congenital variations are not necessarily 

 minute. 



The subject of correlated variations was next mentioned, and 

 their great importance pointed out. A mechanical model was 

 used to explain this matter : it represented an antelope in which 

 when the neck is made to elongate the legs simultaneously 

 lengthen, whilst the horns disappear and the tail shortens. 



The lecturer then gave examples of the successful explanation 



_' Abstract of a Lecture delivered at the London Institution, Finsbury 

 Circus, on February 14, 1889, by Prof. Ray Lankester, LL.D , F.R.S. 



