August, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



203 



tiny holes. These holes are the conceptacles. inside 

 which the eg^gs and sperm are formed. Though most 

 plentiful in early spring- they are to be found all the 

 year round. The fronds with bright orange tips are 

 male and the dull brown ones are female. 



Now, on a bright day when the tide is out we cari 

 easily find tiny drops of brown or orange jelly which 

 have issued from the conceptacles. The one kind con- 

 tains the ova, the other the male elements, and it is 

 now our business to bring these together under the 

 microscope. It is best to break off the tips of the fertile 

 fronds, keeping the sexes separate, and lay them on 

 two dry saucers, placing them in a good draught for 

 some hours. A plentiful supply of mucilage will appear, 

 and if a little of the brown is now added to a single 

 drop of sea-water on a glass slip and examined with a 

 low power, a very pretty sight presents itself. 

 Numerous bags (oogonia) of ova, eight in a bag, are 



FUCUS. (I. I Oogonium legg-casei. 6 cf the 8 ova are visible. 

 (2.) Antheridium with 5permatozoa. 

 (3.) A discharged egg cell with 4 spermatozoa attacking it. 



lying about (Fig. 7). But the rising tide (represented 

 by the drop of sea-water), begins to act on them; the 

 wall of the oogonium disappears, and out float eight 

 beautiful round brown eggs. 



W'tien the orange-coloured jelly is similarly treated 

 — a higher power is desirable — we see large numbers 

 of much smaller cells, which in like manner discharge 

 their contents. But instead of ova we see immense 

 numbers of minute male cells, which no sooner find 

 themselves in the sea (a drop of water is an ocean to 

 them) than they put out two cilia and bep^in to swim 

 hurriedly, and apparently aimlessly, about. We say 

 apparently, for if one of these spermatozoa can succeed 

 in reaching and penetrating a female (egg) cell it will 

 have fulfilled its destiny. Then, and not till then, can 

 the &^% develop to form a new Wrack. 



When, therefore, we add a few ova to a drop of 

 water containing sperm, immediately the male cells 

 cease their aimless wanderings and hasten to the side 

 of the female cell. But why ? They have no eyes to 

 see the beautiful roundness of her form — no senses 

 that we know anything about. They are only tiny bits 

 of protoplasm, and yet there is in them a something, a 

 sentiment — call it chemotaxis or what you will — we, 

 out for a holiday, prefer to regard it as the very germ 

 and essence of the tender passion. Scores, hundreds, 

 of the swimming cells surround the female body, which 

 whirls round and round on its axis, not exactly from 

 giddiness, but from the force of the attentions it re- 

 ceives. At last one of the male bodies penetrates it, 

 fertilization is effected, and the romance is at an end. 



If a number of conceptacles of both kinds, with the 

 mucilage on them, are washed in a basin of water and 

 the contents examined daily, we may trace the first 

 stages in the germination of the fertilized egg cells — 

 and, of course, drazv them. 



Several of the other brown se.uvceds present the 

 same features — with variations. In the .Sea Thongs, 

 the \\hole thong borne by the nuishroom-like frond is 

 beset with conceptacles. Then the number of eggs in 

 a bag varies in different plants. The Knotted W'rack 

 has only four ova in a group, the Channelled Wrack 

 two. These differences are now considered of sufficient 

 importance to warrant the establishment of two new 

 genera. F. nodosics, which we have already seen to 

 differ a good deal from the other wracks, is now 

 Ascophyllum nodosum; and the other is Pelvetia 

 canaliculata. 



A fair average specimen of F. scrratus, selected by 

 chance, had 18 fertile branches that had already dis- 

 charged ova, and 16 others not fully ripe. Of the 18 

 a chance one had over 300 conceptacle pores on one 

 side, and presumably the same number on the other 

 fide. Now, in the course of a single season, the egg- 

 cases, discharged as fast as they ripen, may be put, at a 

 very moderate estimate indeed, at a dozen from a single 

 conceptacle. Each oogoniHm contains eight ova. 

 Total number of ova, without considering the 16 imma- 

 ture branches, considerably over half a million. The 

 extraordinary plenty of the brown seaweeds ceases to 

 be a matter of surprise. The sea near the shore must 

 sometimes teem with ova. They settle down every- 

 where, and at once attach themselves to the rock and 

 begin to develop into new plants. 



Several other brown varieties will be met with which 

 space forbids us to describe. Two very common and 

 very handsome relations of the Giant Tangles, bearing 

 only a single ribbon, and very much smaller in size 

 (Laminaria saccharma and I., hulhosd) are pretty sure to 

 turn up. Then there are several smaller plants, much 

 easier to dry and mount than those we have mentioned, 

 though perhaps less interesting in themselves. 



Here we take leave of the brown seaweeds unless 

 we choose to emulate the " tripper," who carries home 

 with him as a trophy a trailing handful of wrack — a 

 silent monitor, in consequence of its saltness, to warn 

 him of the coming storm. In the next article we shall 

 deal with the " Red Seaweeds," and in it we shall 

 have something to say about collecting and preserving. 



%%%%%% 



TKe Gegenschein acrvd ZodiaLcaLl 

 Light. 



Sirs, — It would be interesting to know whether any special 

 observations have been made, or can be made, on the above- 

 named little-understood phenomena during a total eclipse of 

 the Sun. 



Two theories have been suggested regarding the origin of 

 the Gegenschein. One is that it is the reflection of the Sun's 

 light from meteorites at a distance, which being opposite the 

 Sun are at •' full moon." The other is that it is the forms of 

 the Sun's rays reflected in our atmosphere. Now if the former 

 theory be correct, a total eclipse should not have any material 

 effect upon the appearance, but if the latter, there should be a 

 distinct diminution of light at the moment of eclipse. 



So too with the Zodiacal Light. Some consider it as an 

 atmospheric phenomena, others as a solar adjunct. And 

 much might be done to elucidate this point if careful observa- 

 tions were made during the occurrence of a total eclipse. 



Yours truly, 



P. R. R. 



