June, 1915. 



KNOWLEDGE. 



177 



Antithetic theory of Alternation, the gametophyte, 

 or prothallus, is the direct representative of the 

 Algal ancestor, and the sporophyte, as a separate 

 leafy plant, has arisen de novo. 



The other chief theory regards the two generations 

 as more or less equal from the start, descending 

 from representative generations in the Algae. The 

 sporophyte is thus a direct representative of the 

 asexual generation or phase of the Algae. Generally 

 speaking, the alternation is not very regular in the 

 Algae, and, as Klebs has shown, often depends very 

 largely on external conditions. However, in many 

 cases, as already stated, the sexual act is followed 

 by a definite sequence of events — a post-sexual 

 phase. The independence of the two generations 

 in the Pteridophyte is sometimes regarded as 

 evidence for this — the Homologous theory of 

 Alternation. 



This theory may be applied to the Bryophyta 

 also, but there is no absolute need to regard the 



origin of alternation as the same for both groups. 

 So far as the evidence goes, it seems^to_favour the 

 Antithetic theory for the moss plants, and for those 

 who are generally shy of calling in parallel or 

 analogous descent, this theory seems to be most 

 satisfactory for both groups. Nothing is said here 

 about the highest group of all the Spermaphyta. 

 These are almost certainly derived somehow from 

 the Pteridophyta, but the discussion of this question 

 merits a special treatment. 



From the scanty facts at hand, and the mass of 

 supposition necessary, no one would presume to 

 dogmatise ; and it is perhaps best, while keeping the 

 ideas in sight, to preserve an open mind as far as 

 possible. The true man of science has no right to 

 be pessimistic, but it seems doubtful whether our 

 knowledge will ever enable us to trace the real lines 

 of descent of these. The clues to the problem may 

 be quite lost or obscured, although we trust they 

 are not. 



NOTES. 



ASTRONOMY 



By A. C. D. Crommelin-, B.A., D.Sc, F.R.A.S. 



MELLISH'S COMET.— The following improved orbit 

 of this comet is taken from a Lick Ob'^ervatoyy Bulletin, 

 and is known to be very near the truth : — 



PeriheUon Passage, 1915, July 17-42188, Greenwich M.T. 

 Arc from Note to PeriheUou ... 247° 27' 51" 



Longitude of Node 72 23 47 



Inclination 54 39 30 



Log. of perihelion distance ... -004932 



The comet approaches the Earth wi 

 million miles about June 6lh, and w 

 object in July to southern observers 



thin some thirty-si.x 

 ill be a conspicuous 



The comet returns to the view of English observers 

 about the end of August, when it may still be a naked- 

 eye object. The orbit shows a slight resemblance to that of 

 Comet 1748 II, which was seen only on 1748, May 19th, 

 20th, 22nd, so that the elements are not very well known. 

 Identity of the two comets is perhaps just possible, but not 

 probable. 



SOLAR ACTIVITY is increasing, and a large group 

 crossed the central meridian early in April. A distinct 

 magnetic disturbance occurred a few days later. Father 

 Cortie at the April meeting of the Royal Astronomical 

 Society showed that certain coronal streamers at the eclipse 

 of last August could be explained on the assumption that 

 they were projections of matter in conic sections from the 

 large spot that was then in the disc. In the eclipses of 1893, 

 1898, 1905, 1908, he had established, with lair certainty, 

 connection between the coronal streamers and spots. The 

 connection in 1914 was more doubtful, but still plausible. 



Professor Newall exhibited two spectro-heliograms, 

 wliich vividly illustrated Sporer's law of latitude shift of the 

 zones of solar activity. One, taken by Mr. Evershed in 1907, 

 showed flocculi forming two closely adjacent parallel belts, 

 one on each side of the Sun's equator. The other, taken 

 recently by Professor Newall, showed two belts much more 

 widely separated from each other, about solar latitude 20"". 



POSSIBLE OBSCURE PATCHES IN THE HEAVENS. 

 — Professor Turner has been making counts of the stars of 

 various magnitudes in the published zones of the Great 

 Astrographic Catalogue. He finds evidence of two large 

 regions where there is a notable falhng oflE of faint stars 

 as compared with bright ones, suggesting some great cosmic 

 cloud veiling the hght of the more distant stars. He 

 incidentally expressed the hope that the observatories that 

 have as yet published little or nothing of their zones of the 

 catalogue will endeavour to accelerate publication. It is 

 now nearly thirty years since the scheme was initiated, 

 but there seems small prospect of its completion before 

 1925. Some of the southern observatories have been 

 hampered financially, and several changes have been made 

 in the original assignment of the zones. A conference was 

 to have been held in Paris this year to consider, inUr alia, 

 the acceleration of pubhcation, but owing to the war this 

 has been deferred. 



THE NINTH SATELLITE OF JUPITER.— Mr. Seth 

 Nicholson, the discoverer of this tiny orb, gives a full 

 account of the discovery and of the orbit in Lick Ohservatory 

 Bulletin, No. 265. A plate was exposed on the eighth satel- 

 lite on July 22nd last, the telescope being driven so as to 

 follow it accurately and give a round image, while the 

 fi.xed stars appear as trails. It fortunately happened that 

 the new satellite was in the same region, and movmg at 

 nearly the same speed among the stars, so that it registered 

 itself as a very faint, round dot. It is clear that, if its speed 

 had been different, it would have trailed on the plate, and 

 its image would have been invisible. The stranger was 

 immediately detected on the plate, tliis benig a testimony 

 to the extreme care with which it was examined. It needed 

 exposures on several nights to make sure that it was really 

 a satellite, as there are often llaws that look very like ;istro- 

 nomical bodies. All tests were satisfied, and its character 

 as a satellite was verified, Professor Leuschner's powerful 

 method being used to find the orbit. The following elements 

 were deduced: Node, 309^23'; Omega, 71~' 10'; inclina- 

 tion, 157° 51'; mean anomaly, 1914, July, 27 88, 49° 28' ; 



