4;S 



NA TURE 



[September 13, 1894 



their duplicity at times, cannot be dwelt on here ; but 

 that they are the results of a great inundation, seems to 

 be the conclusion which is most compatible with recent 

 observation. 



A further fact which has recently attracted particular 

 attention is the frequent observation of bright projections 

 on the terminator of the planet's disc. It may be here 

 simply mentioned that the observations as yet seem to 

 point to the presence of high mountains as the cause of 

 these blight markings. 



A discussion of this question will be dealt with, how- 

 ever, in a future article, which will contain a detailed j 

 account of the work up to the present time. 



Such, then, are some of the facts which have been 

 brought before us by the Arizona observations. Observa- 

 tions at other observatories, such as that of Juvisy, iS:c., 

 are also at hand, but the weather seems to have been 

 hard on these eager watchers, so the observations are very 

 few. The surface of Mars is still a puzzle to be unravelled, 

 and there are many who are employed in the fascinating 

 work of solving it. One may repeat, what has often been 

 stated before, that in the study of planetary details, the 

 aperture or the size of object-glass is not the most import- 

 ant function for good observations. .A keen and patient 

 observer sitting at the eye-piece of a comparatively small 

 equatorially-mounted telescope, if he makes his observa- 

 tions carefully and with due regard to atmospheric con- 

 ditions for good seeing, can do more useful and valuable 

 work than one who has a large aperture at his disposal, 

 and employs it indifferently. For Martian detail, .Mr. 

 Lowell puts the observer first, then the atmosphere, and 

 lastly, the instrument, as the order of weights to be given 

 as factors of a good observation. W. J. Lockver. 



Note.— \n my article on "The Discs of Jupiter's 

 Satellites," which appeared in a previous number of 

 this journal (Augi:st ;, p. 320), the table, giving the 

 measurements of the position angle of the ist satellite, 

 requires a slight alteration, owing to a printer's error 

 in that number of Astronotny and Astrophysics from 

 which the table was taken. In the column indi- 

 cating the initials of the observers, the following 

 measures, i, 3, 5, 7, 9, 11, ought to be attributed 

 to Prof. Pickering, and the rest to .Mr. Douglas. This 

 alteration makes no change in the te.xt necessary, as it 

 was only stated that there was " a mean personal correc- 

 tion of about 71, which, in the light of the revised 

 column, still holds good. The correction, with one 

 exception, simply reverses the names of the observers in 

 each case. W. J. L. 



THE ARCHOPLASM AND ATTRACTION 

 SPHERE. 



PI..ATNKR m 1886, when dealing with the spermato- 

 cytes of helix, showed that the great " nebenkern " in 

 these' elements was derived after each division from a 

 coalescence of the spindle-fibres. At the same time he 

 pointed out in the interior of the structure bright re- 

 fractive points answering in every way to what was then 

 known about the cenlrosomes. Some time .ifterw.-irds 

 F. Hermann, in an exquisite description of the karyo- 

 kinetic process in the spermatocytes of salamander, 

 sucressfiilly homnlogiscd the great " archoplasm ''' (as he 

 termed the nebenkern of these cells), on the one hand with 

 Platner's nebenkern, and with the sphere-attractive and 

 archoplasm of Van Ileneden and Boheri on the other. 

 I subsequently drew attention to the fact that this archo- 

 plasm in the salamander arose by a collection of the 

 spindle-fibres precisely in the same manner as that of 

 helix, i.e. these structures (attraction-spheres) in widely 

 separated groups present precisely similar constituents, 

 and arise in a precisely similar way. 



The clear appreciation of the mutual equivalence of 

 these bodies is of considerable value, as it paves a way 



NO. 1298, VOL. 50] 



towards the systematic splitting up of a whole group of 

 structures present in reproductive cells, which had all 

 previously been loosely grouped under the head of 

 nebenkerns. Nevertheless, if we accept it, a certain dif- 

 ficulty arises, to which I referred briefly at the time, and 

 to which Dr. Neves has since called my attention in an 

 interesting letter from Kiel: — If the archoplasm of the 

 spermatocytes with its inner constituents is thehomologue 

 />; /<;/(5 of the attraction-sphere when at rest (Kig. 3, or 

 during the initial phases of mitosis, what is to be said 

 of it in the later phases of this process? 



In the attraction-sphere as first described and ordi- 

 narily understood in ascaris, the centrosomes, with their 

 light-surrounding zone, occupy the middle of an ex- 

 tended archoplasm which divides with the centrosomes 

 during the course of the mitotic change, but in the 

 case of salamander the archoplasm remains un- 

 divided as a rule ; and its whole mass is used up 

 in the construction of the spindle, the centrosomes 

 appearing at the apices of the figure related to a 

 radiation of the non-archoplasmic and external pro- 

 toplasm. Now when the karyokinesis is completed, and 

 the daughter nuclei formed, the centrosomes can be found 

 at the remote sides of the nuclei as in Fig. 4, r, one- 

 half of a dividing spermatocyte of a rat), but the two new 

 archoplasmic masses are being regenerated on each side 

 of the division plane (as in the rat. Fig. 4, h^. These 

 masses become completely formed, but in consequence of 

 their position are destitute of centrosomes, which must 

 acquire a secondary connection with them : so that at 

 this phase the sphere is divided into two pans in each 

 cell, that which attracts (centrosomes) being at one side 

 of the nucleus, that which is regarded as primarily at- 

 tractive (the archoplasmic portion of the kytoplasm) on 

 the other. In salamander these anomalous conditions 

 eventually become righted by the centrosomes wandering 

 round the nuclei into the archoplasm. 



Turning, however, to a still higher type of vertebrates, the 

 Mammalia, a short timeago 1 found in the spermatocytes 

 of various forms, besides other and well-known accessory 

 bodies, a great lightly staining nebenkern (archoplasm), 

 which can be determined as arising during the spermato- 

 genesisby a coalescence of the spindle-fibres (Figs. i,2,<(), 

 so that we must regard this body as having the s.ime value 

 as the nebenkern in Amphibia, in Helix, in Echinoderms, 

 or that it is the archoplasmic portion of the attraction- 

 sphere ; but at no time, either at rest or during active 

 mitosis, does it contain within its mass the centrosomes ! 

 In the resting spermatocytes of the rat (Fig. 2) these 

 I bodies lie quite outside the archoplasm (Fig. 2, t\ they 

 become duplicated, and enter into the formation of a 

 spindle without any connection with the archoplasm 

 (Fig. I, (■;, which passes further aw.y, and ultimately 

 degenerates (Fig. i, a). The spindle- fibres are con- 

 structed anew out of the kyto- and superficial nuclear- 

 plasm, and the mass of substance thus utilised is col- 

 lected on cither side the division plane as the archo- 

 plasmic bodies of the daughter cells. 



The archoplasm, then, has no permanent cxisten( e in 

 these rells, and is of no immediate consequence in the 

 I formation of the spindle. The fact, however, that the 

 transitory body formed in mammals from each new crop 

 j of spindle-fibres, after each division (Fig. 4) rapidly 

 dissolves and reincorporates itself into the surrounding 

 i kytoplasm, is distinctly favourable to the view now 

 gaining ground, tha' the spindle has .1 kytoplasmic origin. 

 From all this it will be seen that we cannot regard 

 the archoplasmic portion of the sphere as a permanent 

 organ of the cell any more than the ripples wind pro- 

 duces arc the permanent features of the surf.ice of a 

 pond. 



On the other hand, all the more recent investigations 

 concerning normal or karyokinetic propagation of cells, 

 whenever sufficient pains have been taken to [insure good 



