March 28, 1878] 



NATURE 



433 



be secured in future investigations of the same kind; 

 nevertheless, it is certain that Lord Lindsay and Mr. Gill 

 have been amply justified by the result in the confidence 

 they placed upon the proposed methods of observation, 

 and have proved that one means of determining the solar 

 parallax, admitting comparatively of very frequent repeti- 

 tion, is comparable in point of accuracy with methods 

 involving far greater difficulty and expense and chance of 

 failure. In the correction of the equations of condition 

 for errors in the tabular places of Juno, derived from 

 observations at Greenwich, Washington, and Cambridge, 

 U.S., it was found desirable to work upon two systems, 

 the probabilities being rather in favour of the second. 

 The definitive result for the mean solar parallax is 8"77, 

 according to the first system, and 8"76 according to the 

 second. To these values and their probable errors 

 (± o""04) the authors do not attach high importance, 

 indeed, a discordant value from observations on November 

 15 being included, they say, " if we were asked what we 

 believe to be the most probable value resulting from the 

 determination, we should reject this result ; the values 

 then become 8"'82 — first system; and 8""8i — second 

 system. At the same time we are aware that the rejection 

 of any observation is quite unsound." In a longer series, 

 however, it is probable, as they observe, that the single 

 discordant value would have been counterbalanced by 

 another. 



So far as we know, this is'the first application of the 

 heliometer to observation in the southern hemisphere. 

 We think it must be generally conceded by astronomers 

 that Lord Lindsay and Mr. Gill have rendered an im- 

 portant scientific service in this introduction of the most 

 accurate of measuring instruments in the investigation of 

 the sun's distance, by a method admitting of such 

 repeated confirmation. Three of the minor planets 

 approach the earth in the present year within the distance 

 at which Juno was observed at the Mauritius in 1874. 



The Satellites of Mars.— Prof. Asaph Hall, to 

 whom, as the discoverer of these bodies, the right of 

 selection of names appertains has definitively decided for 

 Deimus for the outer moon and P hob us for the inner 

 one, agreeably as he mentions to the suggestion of Mr. 

 Madan in these columns, founded on the lines in the 

 " Iliad," which Pope thus renders : — 



" With that he gives command to Fear and Flight, 

 To join his rapid coursers for the fight ; 

 Then grim in arms, with hasty vengeance flies. 

 Arms that reflect a radiance through the skies." 



The Date of Easter. — Easter Sunday falling on 

 April 21, is considered late this year, and it is thirteen 

 days after the mean date, but it is to be remarked that in 

 no year since the introduction of the Gregorian calendar 

 into England has the festival occurred on the latest possi- 

 ble date, April 25, though in two years, 1761 and i8i8,itfell 

 on March 22, which is the other limit. In 1886, Easter 

 Sunday will fall on April 25, in the new or Gregorian 

 style, for the first time since the year 1 734, or eighteen 

 years before this style was accepted in England. The 

 only other occasion since the reformation of the Calendar 

 by Pope Gregory XIII., upon which Easter has fallen on 

 the latest possible date was in 1666, and after 1886 this 

 will not again occur till 1943. 



BIOLOGICAL NOTES 



The Agricultural Ants of Texas.— Mr. H. C. 

 McCook has presented to the Academy of Natural Sciences 

 of Philadelphia a memoir on the habits of these most 

 curious and interesting ants {Myrmica molefaciens, Buckley 

 = M. barbata. Smith). An abstract of the memoir will be 

 found in Sheet 20 of the Proceedings of the above Academy 



(p. 299). The author encamped in the midst of a large 

 number of the ant hills during the summer of 1877, and 

 carefully studied the habits of the inmates ; the spot 

 selected was in the neighbourhood of Austin, Texas, upon 

 the tableland to the south-west of the Colorado River and 

 its affluent. Barton Creek. The limestone rock here and 

 there cropped up, the soil was black and tenacious, vary- 

 ing in depth from a few inches to three feet. The formi- 

 caries were very numerous, and were to be found along 

 roads, in open fields, and in the very streets, paths, 

 gardens, and yards of Austin ; indeed, one was even seen 

 in the stone-paved courtyard of an hotel. They are 

 commonly flat circular clearings, hard and smooth ; 

 a few have low mounds in the centre, composed of bits 

 of gravel of one or two grains' weight ; the clearings 

 vary in width from twelve to two or three feet. From 

 each, roads three to seven in number, diverge into 

 the surrounding herbage. These are often of great 

 length, and during the working hours are thronged by the 

 ants going and returning. The ants take their siesta 

 during the meridian heat of the sun, generally stopping 

 work about twelve, and not returning to it until two or three 

 o'clock. The seeds collected were always taken from off the 

 ground, they were chiefly seeds of small Euphorbiaceous 

 and Rubiaceous plants, and of grasses. The ants 

 proved to be true harvesters. The seeds were carried 

 into the granaries through the central gates. They were 

 shelled, and the hulls were carried out and deposited in 

 refuse heaps, which, when carefully searched, yielded no 

 perfect fruits. They seemed to be most fond of the grass 

 called Aristida stricia, and it even seems possible that 

 they sow this for themselves, though the author does not 

 commit himself to this as a fact. The interior economy 

 of the ant-hill is fully described. Here it may be noted 

 that the ants are clever in attack, that their " sting " is as 

 bad as a wasp's, and that they are so well versed in the 

 science of war, that they would have been more than a 

 match for Mr. McCook, had he not himself employed a 

 small army (of two men) to fight with those ants that 

 would fight with him while he was puUing their granaries, 

 their nurseries, and their queen's palace to pieces, in 

 order to let us know all about them. Prof. Leidy made 

 some remarks on this paper, adding that he had studied 

 the habits of an allied species {M. occidentalis) which he 

 had met with during a summer in the Rocky Mountains. 

 The habits of this species were very like those of the 

 species described by Mr. McCook, but in addition Prof, 

 Leidy mentioned that his species fostered a fine large 

 Coccus for its saccharine production. 



The First Stages of Development in Plants.— 

 Great interest attaches to the earliest changes occurring 

 after the fertilisation of the germinal cell or oosphere in 

 plants ; and the difficulty of the subject has taxed the 

 ability of the best histological botanists. To satisfy the 

 doctrine of evolution many students think it necessary to 

 be able to trace homologies in the development of all stem- 

 bearing plants. The latest investigation, which appears to 

 carry the comparison further than has yet been attempted, 

 is that of Mr. S. H. Vmes, of Cambridge, who has dili- 

 gently sought out and compared all the embryological 

 evidence, derived from the writings of Hofmeister, Han- 

 stein, Fleischer, Mettenius, Pringsheim, and many others. 

 He shows that in all stem-bearing plants the germinal cell 

 (that which is fertilised) divides into two portions, one of 

 which gives rise to an embryonic tissue called suspensor, 

 in higher forms, while the remainder alone produces the 

 true embryo. This comparison is of especial interest in 

 relation to mosses. In these plants it is the spore-capsule 

 which is the product of the fertilisation of the germ-cell, 

 and it is this capsule which corresponds to the whole 

 leafy plant of a fern. Following out the analogy, the seta 

 or stalk of the capsule in a moss corresponds with the part 

 called " foot " in an embryo fern, and with the suspensor 

 in flowering plants. Mr. Vines's paper is contained in the 



