40 



SCIENCE-GOSSIP. 



place to give brief accounts of the bionomics of 

 two species, ' as worked out admirably by those 

 gentlemen. 



On the reproduction of Monas dallingeri Saville 

 Kent. — This is an uniflagellate monad obtained in 

 great abundance in an infusion of cod's-head after 

 keeping it for about three months. It was observed 

 to reproduce itself by three separate methods : 

 (i) by an ordinary process of transverse fission ; 

 (2) spore formation following on the conjugation 

 and encystment of two individuals. The spores 

 produced are of such a minute size as not to be 

 visible under a i^y-inch objective. These two 

 methods by not accounting for the rapidity with 

 which the numbers of the species increased lead 

 to the discovery of the third method. (3) Direct 

 multiple fission. The animal about to divide 

 assumes first a rounded and afterwards an amoe- 

 biform contour. In this state the fiagellum is 

 absorbed. Two line's of division at right angles to 

 one another were then observed to appear, followed 

 rapidly by various others. A quick interchange of 

 the body substance in the various parts then seemed 

 to take place, lasting from ten to seventy minutes. 

 Then this stopped, and the animal split up into 

 a great number of sausage-shaped bodies. These 

 now began to writhe for a space of from seven to 



thirty minutes. The whole mass then fell to pieces, 

 and each portion when it became detached pre- 

 sented the appearance of a tiny uniflagellate monad 

 resembling in all characteristics the parent form. 



On the reproduction of Heteromita rostrata Saville 

 Kent. — The following process of spore- formation 

 following on conjugation is recorded. Under 

 certain circumstances a free-swimming form 

 approaches one which is anchored by its guber- 

 naculum, and completely fuses with it : the nucleus 

 of one unites with the nucleus of the other. In 

 this way an irregular body is formed with two 

 flagella at either end and one central nucleus. For 

 a time this swims about freely, becoming mean- 

 while triangular in shape. The two pairs of flagella 

 are situated at two corners of the triangle. After a 

 time this zygote loses its nucleus, its protoplasm 

 becoming hyaline and transparent. It then settles 

 down to rest and loses all the flagella. After a 

 period of quiescence it undergoes wavelike con- 

 tractions of the surface, and bursts at the three 

 angles. Its contents escape in the form of exceed- 

 ingly minute spores. These increase in size and 

 become oval in shape. The ventral flagellum is 

 first developed, then the anterior end becomes 

 pointed and finally produced into a tractellum. 

 {To be continued.) 



PLANTS AND ANIMALS OF DIFFERENT SOILS. 



By H. Franklin Parsons, M.D., F.G.S.* 



T T must be a circumstance familiar to every field- 

 ■*• naturalist or observant lover of nature that 

 different plants are met with on different soils. 

 Those, for instance, met with on a chalk down are 

 almost entirely different from those on a gravelly 

 heath or in a marshy meadow. Again, the presence 

 of certain animals depends upon the existence of 

 locahties suitable for their habitation, or of the 

 plants necessary to them as food. The subject is 

 one for which I can claim no sort of originality^ 

 but I hope that an amplification of the text which 

 I have chosen may not be without interest as 

 illustrating the links which connect the different 

 branches of natural history studies. My remarks 

 refer especially to south-eastern England. 



In classifying soils for our purpose, we have to 

 regard them from several points of view. We 

 have to consider the top soil or surface mould in 

 which terrestrial plants take root ; also the subsoil, 

 from the disintegration of which the surface soil is 

 mainly formed, and upon the nature of which the 

 character of the latter greatly depends. We may 

 classify the subsoil according to its geological age, 



* Being a paper read before the Annual Congress of the 

 South-Eastern Union of Scientific Societies at Croydon, 

 June 3rd, i8g8. 



distinguishing the deeper strata upon which the 

 general contour of the country mainly depends, and 

 the more superficial strata or "drift" by which 

 the character of the surface soil is often modified. 



As regards their physical characters, rocks and 

 soils may be grouped according to their hardness 

 or softness ; perviousness or imperviousness to 

 water ; dryness or moisture ; and into light or 

 friable and heavy or retentive soils. 



As regards their chernical composition, subsoils 

 may be classified as : (a) hard crystalline rocks, 

 as granite and slate — these are not represented in 

 the south-east of England ; (i) calcareous, as 

 chalk, the harder limestones (of which also we 

 have no representative in the south-east of 

 England) and marl ; (c) silicious, as sand, sand- 

 stone and gravel ; (d) argillaceous, clay and shale ; 

 (c) peat ; (/) soils of mixed character, as alluvial 

 loam and boulder clay. 



From an economic point of view, there is also 

 the division into fertile and poor soils. The 

 qualities which render a soil valuable for agri- 

 cultural purposes are the depth of surface soil, 

 its richness in nitrogenous organic matter and in 

 readily soluble mineral constituents, and its aeration 

 and nitrifying properties — the latter being due to 



