SCIENCE-GOSSIP. 



in later years, to revive the art in Britain. Even 

 now Bewick's pictures are admired to the full, and 

 his style frequently copied, although the art is, 

 unfortunately, disappearing before the more rapid 

 and less expensive " process " illustration so 

 generally used. Bewick died on November 8th, 

 1828, at his house in West Street, Gateshead. In 

 character, Thomas Bewick seems to have been a 

 thoroughly upright, honourable man, unassuming, 

 but very independent and industrious. He brought 

 up his son Robert Elliot Bewick (1788-1849), to 

 his own profession of wood-engraver, in which 

 Robert was most successful. He designed and cut 

 many of the characteristic tail-pieces which adorn 

 the works of Thomas Bewick. 



There are several portraits of Thomas Bewick in 

 the neighbourhood of Newcastle-on-Tyne where 

 the family name is deeply cherished. There are 

 two in the National Portrait Gallery, the one 

 sketched here by Miss Hensman being an oil 

 painting by Thomas Sword Good. It was presented 

 to the Gallery in 1894 by the Rev. Albert A. Isaacs, 

 M.A., of Corpus Christi College, Cambridge. In 

 it Bewick is represented about life-size showing 

 hardly more than the head. He appears to have 

 been a man with well defined features, though a 

 little hard and stern-looking. His complexion is 

 depicted as florid, hair black, turning to iron-grey. 

 (To be continued.) 



COMMENSALISM AND SYMBIOSIS. 

 By James Burton. 



TT is a matter of common knowledge that 

 frequently, both among plants and animals, 

 a kind of companionship is maintained between 

 two organisms. This is sometimes of advantage 

 to one only of the two parties, but often both 

 profit by the association. The companionship 

 may range from mere accompaniment to that of 

 the most intimate connection. When the two 

 organisms may dwell the one within the other so 

 as to form apparently but one body, the partner- 

 ship is known as Commensalism or Symbiosis, 

 the former term being used generally for the 

 connections of the less intimate kind, while the 

 latter is restricted to those cases where the organ- 

 isms have a closer union. It is at the same time 

 true that no sharp line can be drawn dividing the 

 one form from the other, as all intermediate states 

 exist. Commensalism (which means having the 

 same table) is well illustrated in its less intimate 

 form by the Echeneis or sucking-fish, which 

 accompanies other fish, sharks especially, no 

 doubt profiting by the unconsidered trifles it picks 

 up from the meals of its voracious messmate. It 

 is able by means of a sucker on the top of its head 

 to fix itself to the body of its friend, and thus gets 

 conveyed from place to place without the expendi- 

 ture of any exertion. Some sea anemones seem 

 particularly inclined towards commensalism ; they 

 are often found attached to the shells forming the 

 homes of hermit crabs and even on the carapaces 

 or claws of crabs, to an extent masking the animals 

 on which they are fixed, and gaining in i-eturn a 

 change of situation advantageous in the require- 

 ment of food. They also themselves occasionally 

 become the homes of tiny fishes which dwell within 

 the cavity of their body. Some species of Holothxiria 

 (sea slugs), and a small fish, the Fierasfcr, live in 

 amicable and close companionship ; the latter 



inhabiting the interior of the former, but passing 

 in and out as it finds requisite. A crab, Pinnotheres 

 pistivi, is frequently found inside the shells of 

 various bivalves, among others the mussel, where it 

 obtains shelter and apparently does its host no harm, 

 though probably scarcely paying for its accommo- 

 dation in the way believed by the ancients, who 

 asserted that it warned its friend of coming danger 

 by a gentle nip, and so got the valves closed in 

 time to ensure mutual safety. 



Some of the most interesting and typical cases, 

 complete in all details, are to be found in Mr. 

 Thomas Belt's " The Naturalist in Nicaragua. ' 

 If space permitted I should like to reproduce some 

 of his observations, but they are too extensive. 

 Anyone caring for natural history matters could 

 not do better than procure this work. To take one 

 instance — the trunk and branches of a species of 

 acacia bear numerous pairs of strong curved spines, 

 shaped something like a bull's horns. These, 

 when first produced, are soft and filled with a 

 sweetish pulpy substance, which is soon eaten 

 away by a small ant [Pscudomyrma), which makes a 

 hole near the end of the spine and, after emptying 

 it, dwells inside. " Here they rear their young, 

 and in the wet season every one of the thorns is 

 tenanted, and hundreds of ants are to be seen 

 running about, especially over the young leaves." 

 If the plant is shaken or a leaf injured the ants 

 swarm out from their homes and attack the 

 aggressor, and are able to bite and sting severely. 

 They thus form an efficient protection for the 

 plant both against browsing mammals and also 

 against the leaf-cutter ants, which are terrible foes 

 to vegetation in general in that region. In return, 

 the ants are not only supplied with houses and 

 partial food by the acacia as described, but in 

 addition certain glands situated on the leaves, 



