290 



NATURE 



[October 28, 1920 



Many entomologists will welcome an important 

 paper by Mr. A. C. Baker on the classification of 

 Aphidae which has been issued lately as Bulletin 

 No. 826 of the U.S. Bureau of Entomology. Probably 

 no group of insects has received more attention from 

 the economic point of view than aphides or plant-lice. 

 Unfortunately, the classification and synonymy of 

 aphides are in a chaotic condition, and great difficulty 

 is often experienced in securing correct naming of 

 specimens. Mr. Baker's paper deals with their generic 

 classification, and was undertaken with the object of 

 remedying this defect, to some extent at least. He 

 regards these insects as constituting the super- 

 family Aphidoidea, and his efforts are confined to the 

 genera and tribes of the family Aphididae ; Phylloxera 

 and its allies he considers to be a separate family. The 

 genus Mindarus is regarded in some respects as the 

 most primitive of all forms, while the Hormaphidini 

 are considered to be the most specialised. The last- 

 named insects are gall-formers ; they lack the cornicles 

 or honey-tubes, and have curious aleyrodiform genera- 

 tions. The systematist who desires to make real pro- 

 gress with the specific determination of many aphides 

 will have to rear each individual species and note 

 carefully the characters of each generation for a given 

 food-plant. The labour involved would be great and 

 the time demanded lengthy, but the progress made 

 would be sure, and substantial biological knowledge 

 would result. 



The problem of the toxic action of sulphur used 

 as a fungicide is being investigated at the Agricul- 

 tural and Horticultural Research Station, Long 

 .^shton, Bristol, and a preliminarv report . on the 

 subject by Messrs. B. T. P. "Barker, C. T. 

 Gimingham, and S. P. Wiltshire appears in 

 the station's annual report for iqio, recently re- 

 ceived. It has frequently been noticed that flowers 

 of sulphur applied in paste form to the hot-water 

 pipes in greenhouses will keep in check diseases 

 of the mildew type on plants in the houses. Further, 

 there are records of cases of unsprayed gooseberry 

 bushes which have been defoliated as a result of the 

 lime-sulphur spraying Of adjacent plots of bushes. 

 The results suggest that the toxicity of the spray 

 is due to some gaseous compound, and if such a 

 compound could be discovered it might be possible 

 to surround plants with an atmosphere sufficiently 

 antiseptic to prevent disease. The nature of the 

 changes which follow the application of a sulphur 

 sprav w-ere, therefore, studied, and the results showed 

 that the active agent is the finely divided sulphur 

 which is formed by the decomposition of the spray 

 fluid. Several theories have been advanced to explain 

 the action of this sulphur; 'the toxicity may be due 

 to the gradual oxidation of the sulphur to sulphur 

 dioxide, to the formation of sulphuretted hydrogen, 

 to conversion into sulphuric acid, or, finally, the 

 sulphur may act of itself by its own vapour. The 

 experiments at Long Ashton show that under 

 ordinary practical conditions none of these hii'po- 

 theses meet the case. Further experiments have been 

 made, and it is hoped that these will demonstrate the 



NO. 2661, VOL. 106] 



method by which sulphur at a distance from the 

 plants under treatment is brought into contact with 

 the fungus. It then remains to discover what happens 

 when the sulphur comes into contact with the fungus, 

 and for this purpose further researches must be made. 



Prof. Jean Massart records (Bull. Acad. Roy. 

 Belgique, Classe des Sciences, 1920, Nos. 4-5) the 

 results of his observations on the movement of 

 different species of littoral flagellates, and gives 

 numerous figures of the organisms and of their paths 

 of movement. Several of the genera and species 

 observed are new, but the systematic descriptions 

 will be published later. In Podomastix (a new genus) 

 the pseudopodia — one to four in number — are long 

 and slender, uniform in thickness, sometimes 

 branched, and movable in an oar-like manner. They 

 are retractile, and represent a transition between 

 pseudopodia and flagella. The two flagella of Cerco- 

 bodo primitiva, n.sp., are tapering prolongations of 

 pseudopodia, but, contrary to those of Podomastix, 

 they are permanent. One of the flagella is anterior 

 and serves for swimming, the other is directed pos- 

 teriorly. This organism can also move forward by 

 lashing its anterior flagellum, its posterior flagellum 

 and part of its body being applied to some object over 

 which it is progressing, and, finally, it can move in 

 amoeboid fashion. The author remarks that many 

 of the flagellates exhibit these three kinds of loco- 

 motion. Clautriavia mobilis, which has a single 

 flagellum directed backwards, never swims freely ; it 

 becomes applied to some object by the flagellum, and 

 pushes itself forwards obliquely, first right, then left. 

 Dimastigamceba, n.g., forms pseudopodia while 

 swimming freely and while creeping. In the latter 

 condition the two flagella trail behind. The reaction 

 —acid or alkaline — of the surrounding fluid was 

 found to play an important part in determining 

 change of form with Eugleninse. In a slightly acid 

 fluid these organisms swim in a state of extension 

 and without modifying their contour, but if the 

 medium is rendered alkaline the swimming is 

 arrested and the organisms exhibit diverse changes 

 of form. 



The latest issue of the Journal of the Marine Bio- 

 logical Association (No. 2, vol. xii.) contains several 

 papers dealing in considerable detail with the life- 

 histories and food of Teleostean fishes. Particularly 

 noticeable is a paper (promising further contributions 

 to the subject) on the physical conditions influencing 

 breeding in marine organisms, breeding being defined 

 as "fertilisation resulting in subsequent development." 

 There is much experimental and observational work 

 in the literature of biology, and Dr. Orton collates 

 and discusses some of this. The breeding of a marine 

 animal is usually seasonal, and may occur during a 

 very limited part of the year, or it may be con- 

 tinuous (in some tropical and abyssal organisms). 

 It may begin at a very early period in the life of an 

 animal, be repeated annually, or even be delayed 

 until almost the end of life, and may occur only 

 once. It is very diflicult to correlate the nature 

 and abundance of food with the occurrence and dura- 



