486 



NATURE 



[December 9, 1920 



Prof. R. W. Hegner discussed the relations of 

 nucleus, cytoplasm, and external heritable characters 

 in the genus Arcella, in which the nuclei can be seen 

 and measured in the living animal and the chromatin 

 mass accurately determined. Pure lines of Arcella 

 dentala, obtained during vegetative reproduction from 

 "wild" specimens by pedigree breeding methods, dif- 

 fered from one another in size and spine-number, 

 which are closelv correlated — the larger the .shell, the 

 greater the number of spines. These two characters 

 were found to be correlated also with chromatin 

 mass, for uninucleate descendants of halves (obtained 

 bv cutting into two) of binucleate animals were only 

 about half as large as binucleate Specimens belonging 

 to the same line. The uninucleate descendants of 

 halves of binucleate specimens always regained tlie 

 binucleate condition after a few generations. The 

 later descendants were always binucleate, but the 

 size and spine-number of the typical binucleate were 

 reached onlv after three or four more generations, 

 during which the di.nmeter of the shell and the 

 number of spines increased gradually, i.e. the great 

 change within — the doubling of the chromatin mass — 

 was accompanied externally by small changes in a 

 definite direction. If the internal condition had not 

 been known, the conclusion would have been reached 

 that the change in external heritable characters was 

 due to several gradual modifications instead of to one 

 large mutation. 



Messrs. E. Heron .Mien and .^. Knrland read a 

 paper on protoplasm and pseudopodia, based on 

 observations on Foraminifera. Thev conclude that 

 protoplasm is capable of almost unlimited extensibility 

 and attenuation bv imbibition of water, and that 

 pseudopodia are not extended as such, but formed 

 from protoplasm surrounding the shell. They claim, 

 for the pseudopodia a rudimentary nervous reaction 

 to stimuli. 



Prof. Kofoid exhibited a serios of plates for a forth, 

 coming monograph on the unarmoured Dinoflagel- 

 lata, and Miss C. Herdman exhibited living specimens 

 of .Amphldinium from Port Erin. 



The Influence of Salts on Groivth. 



Dr. Cresswell Shearer read a paper on the influence 

 of salts on growth. He described experiments which 

 show that living bacteria offer considerable resist- 

 ance to the passage of ions of various salts ; dead 

 bacterial protoplasm offers no resistance. There is 

 something peculiar to the living state that conditions 

 this resistance, and this should be kept in mind in all 

 applications of the results of protein chemistry to 

 living protoplasm. 



Annelids. 



In a communication on the polyphyletic origin of 

 genera in the 01igocha."ta and its bearings. Prof. J. 

 .Stephenson showed that the genera of the Megascole- 

 cidae can be arranged in the form of a phylogenetic 

 tree. The differentiating characters are few, e.g. in 

 the majority of genera of the sub-family Megascole- 

 cinae they concern only the setae, prostates, and 

 nephridia. The evolutionary changes in these systems 

 have demonstrably taken place more than once, and 

 the differentiating characters and their various com. 

 binations are few enough to render it probable that 

 the same combination, i.e. the same genus, has been 

 reached in more than one way. ,'\part from prob- 

 ability, there is anatomical and geographical evidence 

 that the genus Megascolex has arisen from both 

 Notoscolex and Porionv.x, and from N'otoscolex more 

 ■than once. The multiple origin of Microscolex from 

 Notiodrilus has also been demonstrated, and there is 

 some evidence of the multiole origin of Pontodrilus. 



NO. 2667, VOL. 106] 



To assert the polyphyletic origin of a genus is, how- 

 ever, unorthodox ; writers obviate it by merging the 

 genera concerned, but this is to evade' the dimculty. 

 Ihe answer given to the question of polyphyly has 

 a bearing on geographical distribution. A number of 

 genera of the sub-family Megascolecinae occur both in 

 India and Australia; the Octocha'tinse occur only m 

 India and New Zealand. These distributions are 

 explained by assuming land-bridges between India 

 and Australia and between India and New Zealan I. 

 Hut such connections cannot have ejtisted since tlie 

 Eocene, or Eutherian maiymals would have entered 

 Australia and New Zealand. Earthworms are, how- 

 ever, a recent group, and, such a genus as Megascolex 

 is among the phylogenetically youngest earthworms; 

 its origin, and probably that of other genera common 

 to the two regions, must have been recent (since the 

 Eocene). Land connections are thus apparently in- 

 sufficient to explain the distribution, and a double 

 origin of at least the phyletically younger genera 

 seems worthy of consideration. 



Prof. Pierre Fauvel sent a summary of the results 

 of his examination of the marine annelids collected 

 in the Abrolhos Islands by Prof. Dakin. Sand- and 

 mud-dwelling Polychaeta were absent; .Aphroditida; 

 and Eunicidae were plentiful, together with .Amphino- 

 midae and a few Nereida — ^^a small fauna of Poly- 

 chaeta creeping on the jtones and corals. Of the 

 nineteen species from the .Abrolhos, five are known 

 only from the warmer parts of the Indian Ocean, 

 eleven belong to the tropical area, but often ejftend 

 beyond it northwards and southwards, and three belong 

 to the Australian coast. The Polychaet fauna of the 

 .Abrolhos is probably the same as that of most of 

 the coral-reefs of the Indian Ocean, with the addition 

 of a few species belonging to the Australian coast. 



Hookworm and Human Efficiency. 



Prof. Kofoid, in an address on hookworm and 

 human efficiency, described investigations made in 

 the United States .Army in connection with the 

 elimination of hookworm infection among recruits. 

 Examination revealed an infection of about lo per 

 cent, among men from the Southern States, and a 

 slicfhtlv higher rate among whites than among blacks. 

 .A statistical investigation of the incidence of disease 

 among 24,000 men at Camp Bowis, Texas, over a 

 period of eight months (Including that of the measles- 

 pneumonia epidemic of the winter of 1017-18) showed 

 that men in whom hookworm infection had been 

 det'^cted had a much higher sick-rate, and were nior(- 

 often sent to hospital for severe infections. Regiments 

 with more than 10 per cent, infection by hookworm 

 had a much higher death-rate from pneumonia than 

 regiments with less than 10 per cent, infection bv 

 the worm. A comparison of the mental ratings ob. 

 tained bv the tests of the Psychology Board of the 

 U.S. Army in the case of 10,000 recruits from the 

 hookworm area showed that white able-bodied men 

 with hookworm infection have a lower average ratinn^ 

 than men in whom the infection was not detected. 

 The mental deficiencv thus measured was nearlv 

 7K, per cent., and affected all grades of intelligence 

 from the highest to the lowest, but the latter some- 

 what more severelv. Hookworm infection, even in 

 cases when it is light, is a matter of great educa- 

 tional, sanitary, and economic importance. 



Physiology of Migration. 



Prof. .A. Meek discussed the phvsiologv of migr.i- 

 tion. He stated that the passive denatation of the 

 egg, larval, and young stages of fish may be. and 

 usually is, succeeded bv an active down-current migr.v 



