I50 



NATURE 



I'/une 12, 1879 



all collectors of marine plants. It is composed'of branched 

 filaments made up of large cylindrical cells placed end to 

 end in a single row. When it is in fruit, the filaments are 

 furnished with short branches terminated by a globular 

 involucre, in the interior of which are ranged the repro- 

 ductive bodies. How are these formed, and how do these 

 filaments and appendages grow ? What modifications do 

 the cell-contents experience during this formation and 

 growth ? These are the points explained with a good 

 deal of clearness by Dr. Wright in the first of the two 

 latter memoirs referred to (on the cell-structure of G. 

 setacea, and on the development of its antheridia and 

 tetraspores). Referring to the memoir itself for details, 

 I •would only call attention to a peculiarity noticed in 

 the development of the involucre. The rays which 

 compose it take their origin in a circle from the penulti- 

 mate cells of particular ramuli, formed by a small number 

 of cells and slightly club-shaped at their superior extre- 

 mity. These rays are not all at once free. Detached 

 from the protoplasmic mass on which the apical cell reposes, 

 they for a long time increase underneath the common 

 membrane which clothes the frond, and they are only 

 made free somewhat later on by the rupture of this 

 membrane. First of all figured, but very imperfectly by 

 Derbes and Soher, well represented from life by Thuret, 

 this peculiar disposition is shown by Dr. Wright as made 

 clear by the use of reagents, and it would appear to be 

 equally met with in the genus Pandorea, recently described 

 by J. Agardh. 



In following from their first appearance the develop- 

 ment of the reproductive organs on the rays of the 

 involucre, Dr. Wright observed that the cells destined by 

 their origin and their position to form the tetraspores, 

 did not all comport themsclres in the same manner. 

 Some of them produced the ordinary four spores, but in 

 the interior of the others globular cells arose provided with 

 a beak, from which there came out colourless corpuscles, 

 wonderfully like the antherozoids of the FlorideK. The 

 resemblance of these bodies to species of Olpidium 

 did not escape Dr. Wright, but struck by their constant 

 presence on the specimens which he examined, by the 

 regularity with which they appeared on determined points 

 of th« involucre, he thought they might be regarded as 

 the antheridia of Criffithsia setacea, and here he has over- 

 looked the fact that true antheridia, of the ordinary type 

 in the Florideae, had long since been described and figured 

 in this very species by Thuret {Ann. des Sc. Nat. 3 ser. 

 Bot. Tom. 16). On this occasion Dr. Wright, however, 

 records an observation as new as interesting, viz., that he 

 has seen the corpuscles as they left these wrongly imagined 

 antheridia perform movements after the manner of 

 amoebae. 



In the second of the two memoirs, having for its title 

 "On the Formation of the so-called 'Siphons,' and on the 

 Development of the Tetraspores in Polysiphonia," the 

 author describes with much care the method of the for- 

 mation of the frond in Polysiphonia urceolata, and very 

 exactly proves the relationship existing between the "tube 

 central" and the "siphons," and between the siphons 

 themselves. For a great part he therein only confirms 

 the results of those preceding him in such inrestigations, 

 for the history of the development of the frond in Poly- 

 siphonia has been almost exhausted by the works of 

 Naegeli, Kny, and Magnus. I am almost afraid that an 

 analysis of these minute details would inspire the reader 

 with that horror which, according to Naegeli, such morpho- 

 logical researches bring with them to the systematic 

 botanists, but I cannot bring myself to omit extracting 

 the following passage, in which some curious vital pheno- 

 mena are incidentally described by Dr. Wright, as he 

 found them to exist in the cells of Bryopsis. 



" Under the influence of some local irritation, which 

 must not be enough to injure the cell wall of the speci- 

 men under examination, the denser portion of the proto- 



plasm will often be found to draw itself from the upper 

 part of these cells. As it does so, the very conspicuous 

 chlorophyll granules will be seen to be drawn together 

 until they become pretty tightly packed. There is an 

 apparent rounding off of the upper portion as it gets 

 drawn -down in the tube of the cell wall, and under a low 

 power of the microscope this convex surface seems pretty 

 sharply defined ; but turn on a high quarter of an inch or 

 an eighth of an inch objective, and a very remarkable 

 phenomenon will present itself — for there will then be 

 seen a mass of pseudopods not easily to be forgotten and 

 difficult to describe under any other name ; they stream 

 away from below the apex of the cell wall, converging 

 downwards until they are lost in the centre of the convex 

 margin of the withdrawing mass of protoplasm. Here 

 they are broad, while towards the apex of the cell they 

 disappear through their very tenuity. Coursing down 

 along these pseudopods, very minute granules can be, on 

 careful focussing, detected ; these are ultimately lost in 

 the denser protoplasmic mass which engulphs them. This 

 streaming goes on for a while, until all the protoplasm ot 

 a certain density is drawn into the lower mass ; this then 

 finally rounds itself off and forms an independent cell 

 wall in front, which of course will be below the former 

 growing point of the cell. There is apparently no plastic 

 protoplasm remaining above this — no small disc even of 

 homogeneous mucilage to be seen ; all the viscid proto- 

 plasm seems to have gone to the rear, and it would appear 

 as if the upper portion should now become sphacelated — 

 perhaps disappear — and a new apical growth proceed 

 from below it ; but this is not so ; there is life in the front 

 still ; it goes on growing as before, and in process of 

 time it will be found to leave in its rear dense chlorophyll- 

 bearing protoplasm, and so on through the several layers 

 until x\ic puncium itself is, as before, reached." 



OUR ASTRONOMICAL COLUMN 



Biela's Comet. — As bearing upon the possible re- 

 turn of Biela's comet during the latter part of the 

 present year, it will not be out of place if we here sum- 

 marise the results of an investigation made by Prof. 

 Oppolzer in 1873, on the possible connection of the comet 

 discovered by Mr. Pogson at Madras on December 2 

 previous, with Biela's comet and the great meteoric 

 shower of November 27, 1872. It will be remembered 

 that the comet in question was found in consequence of a 

 telegram sent by Prof. Klinkerfues to I\Iadras immediately 

 after the meteoric display, to the effect that Biela' s comet 

 had " touched the earth " on the evening of November 

 27, and urging Mr. Pogson to search for it near the star 

 6 Centauri. From the Madras observations on the nights 

 of December 2 and 3 (the only occasions on which the 

 weather was favourable), as they were first approximately 

 reduced, Oppolzer derived the following data : — 

 1872, December 3"o M.T. at Berlin. 



..:S7'-o.^ = 



+ 46' -3. 



Comet's geocentric longitude (A) 223 I5"6 



,, ,, latitude (/3) - 20 lO'O 



And the unit of time being a mean solar day, 

 d\ 

 dt 



At a subsequent time Mr. Pogson published more 

 accurate positions of the comet than those at first com- 

 municated, which would give the following similar data, 

 differing, it will be seen, in no material degree from those 

 adopted by Oppolzer : — 



1S73, December 3-0 M.T. at Greenwich 



1 



A ... 223° 2l''I /3 ... —20" 8''6 



+ 46'-4 



It had soon been found, as might have been expected, 

 that no satisfactory conclusion could be arrived at by 

 comparison of Michez's elements of Biela's comet with 



