164 



KNOWLEDGE 



[September 1, 1893. 



There are other less well-known representatives of this 

 group which we have not space to notice ; and we 

 accordingly pass on to say a few words about dolphins — a 

 term which should be restricted to those forms having a 

 distinctly marked beak. Since, however, sailors will 

 persist in speaking of dolphins indilterently, either as 

 bottle-noses or porpoises, the inexperienced landsman 

 must accordingly be on his guard not to confound them 

 when thus spoken of either with the bottle-nosed wbales 

 or the true porpoises. Dolphins, which are divided into 

 numerous genera, according to the number of their teeth, 

 the length of the beak, and other characters, are all 

 comparatively small species, seldom exceeding some ten 

 feet in length ; and while the great majority are mai-ine, a 

 few ascend some of the larger tropical rivers, such as the 

 Amazon. Fish of various kinds constitute their usual 

 prey ; but one peculiar species recently described from the 

 Cameroous district is beheved to subsist on sea-weed. Of 

 the better-known types, the common dolphin represents 

 the genus Del/iliviKs, the bottle-nosed dolphins constitute 

 a distinct genus (Tursiops), yvhile the long-beaked dolphins 

 are separated as Steno. 



To the foregoing group of beaked dolphins the ordi- 

 nary observer would, doubtless, be disposed to refer three 

 peculiar species severally restricted to the larger rivers of 

 India, the Amazon, and the mouth of the La Plata river, 

 but as these diiier more or less markedly from other 

 dolphins in certain structural features they are referred to 

 a distinct family. Moreover, since these pecuHarities 

 approximate to a more generalized type, while their fresh- 

 water habits and scattered distribution indicate extreme 

 antiquity, it is not improbable that these three dolphins 

 are the most primitive of all existing cetaceans. At 

 present we have, indeed, no evidence of fossil forms allied 

 to the susu or Gangetic dolphin {Platanista) ; but in the 

 older tertiary deposits, both of the United States and 

 Europe, there occur the remains of dolphins evidently 

 nearly allied to the two existing South American species 

 (In'ui and StenodelpJus), and thus clearly proving the 

 antiquity of those types. It is almost superfluous to add 

 that it is most probable that the ancestors of the cetaceans 

 which first took to an aquatic life were inhabitants of 

 fresh-water, and it is therefore only what we should expect 

 that the most primitive of the existing representatives of 

 the order were likewise of fluviatile habits. 



GALLS AND THEIR OCCUPANTS.-IIL 



By E. A. Butler. 

 (Continued from page 146.) 



LEAVING now the oak tree, which we have found 

 so rich in the products of gall insects, and looking 

 about in other directions, we find very few galls 

 formed by the true gall-flies (Ci/tiipnhp) that are 

 sufficiently common and conspicuous to have 

 obtained popular names, and only one or two need be 

 referred to. Everyone is, of course, familiar with the 

 bright crimson or greenish-red mossy balls which often 

 appear on the wild rose bushes, and which, formerly known 

 as "briar-balls," and still dear to the heart of childhood 

 under the name of " robin's pincushions," form one of the 

 prettiest ornaments of English hedgerows. These, too, 

 are galls originated by a Cynlpid, a gall-fly which, though 

 itself of no great beauty, yet owns as its home the most 

 elegant of these fairy-like structures. In this instance, 

 the swollen mass of tissue forming the gall proper is 



Fig. 7. — Sectiou of Bedeguar 

 of Rose, showing two cells, 

 one containing larva of G-all- 

 flv. 



completely concealed by a quantity of moss-like filaments 

 (Fig. 7) like those that envelope the buds of moss roses ; 

 these filaments run out from 

 the entire siirface of the gall. 

 Each " pincushion " contains 

 a family of the gall-fly (E/iodites 

 roxir), and if they are picked 

 when fully ripe, there is no 

 difficulty in rearing the little 

 red-bodied fly from them. The 

 gall insects, however, are sub- 

 ject to the attacks of a pretty 

 ichneunwH fly, which is also 

 red - bodied, and hence one 

 must not too readily conclude 

 that any transparent winged 

 creatures that issue from the 

 mossy ball are its legitimate 

 inhabitants. But if attention 

 be paid to the number and 

 arrangement of the nervures of 

 the wings, and to the shape of 

 the body, as described in a former paper, there will be no 

 difficulty in determining whether it is the BhodiUs or its 

 parasite that is escaping from the gall. 



This gall is also known by the name " bedeguar," 

 though that name belonged in the first instance to another 

 object and was incorrectly applied to this. The word is 

 an Arabic one, and originally signified the thorny white 

 flower of a kind of thistle. But, apparently in consequence 

 of a misimderstanding as to its etymology, it was thought 

 to mean some growth connected with a rose tree, and 

 hence was applied to the gall in question. Under the 

 name bedeguar, therefore, the gall was sold in the shop of 

 the apothecary as a drug, and was considered a specific 

 against various serious ailments, being for this purpose 

 ground up and administered as a powder. Its medicinal 

 use is of long standing, and Pliny recommended that it 

 should be mixed with honey and wood-ashes before being 

 taken. 



In this rose gall there is not such a disparity in the 

 numbers of the sexes as is found in the various galls of the 

 oak. So far from there being always a preponderance of 

 the female element, the ease is sometimes reversed — e.ij., 

 from three galls of bedeguar, Schlechtendal once bred thirty- 

 two males and only two females ; but the experience of 

 collectors is not uniform in this matter, and Mr. Cameron 

 records a proportion strikingly the reverse — viz., one male 

 to one hundred females. But though males are known 

 and are sometimes numerous, still the insect follows the 

 usual law of the group, and parthenogenesis is not in- 

 frequent. 



On the under surface of the leaves of wild roses may 

 frequently be seen beautifully coloured, berry-shaped galls, 

 which, save for their opacity, forcibly recall the currant 

 galls of the oak. Some are quite 

 spherical, others consist of globes 

 with three or four long and sharp 

 spikes projecting from them, and re- 

 mind one of the spiked balls carried 

 at the end of the warlike clubs and 

 maces of olden times. All these 

 galls belong to the same genus as 

 the bedeguar, but each contains only 

 a solitary fly. If cut open, they 

 will be found to be very thin-walled 

 and to have, therefore, a large central cavity (Fig. 8, a) ; 

 at least this is their condition if they are free from 

 parasites, and the gall-fly is allowed to develop naturally. 



Fio. 8.— Sections of Gall 

 of Jihi/diips eylauterirt. 

 A, normal ; H. when 

 containing inqnilines. 

 (.Vftcr Fitch.) 



