344 



SCIENCE. 



[Vol. I., No. 12. 



Action of light on Algae. — Berthold has made 

 a minute study of the action of light on seaweeds, 

 especially Florideae, and gives the results of his ob- 

 servations on species growing near Naples, and of his 

 cultures made at the zoological station in that city. 

 Under the Influence of feeble illumination, the species 

 studied turned towards the light; but, when stronger 

 light was used, they turned from it. He considers, 

 in detail, the effect of light in modifying the growth 

 and branching of different species. Many seaweeds 

 are, at some seasons of the year, covered with color- 

 less hairs, whose function has hitherto been supposed 

 to be connected with absorption of nutritive material. 

 Berthold denies this supposed office of the hairs, and 

 maintains that they act as a protection against too 

 bright light, and states that exposure to light is fol- 

 lowed by an increase in the growth of hairs. He 

 also gives an explanation of the iridescence of certain 

 species, which is produced by the formation of small 

 plates on the outer part of the cells, as in Chylocla- 

 dia, or by globular or irregular bodies in the cells, as 

 in Chondria and Cystoseira. He denies the existence 

 of any true fluorescence in such cases, which he con- 

 siders to be merely instances of iridescence, and as- 

 serts that the plates and globules act as shields against 

 too strong light. He also attributes a similar func- 

 tion to the calcareous incrustation found in Chara and 

 seaweeds like Acetabularia and C'orallina. — {Priiig- 

 sheim'sjahrb.) w. g. p. [724 



Fertilization of red seaweeds. — Professor Fr. 

 Schmitz has published some general observations on 

 red seaweeds, in which he advances the view that 

 the thallus in this group of Algae is always of a fila- 

 mentous origin, no matter what the cellular charac- 

 ter of the nfature frond may be, and secondary cell- 

 divisions never include the axis of the primary cells. 

 He considers, in detail, the fertilization and the for- 

 mation of the carpospores, and is of the opinion that 

 there is no indirect impulse transferred from one cell 

 to another at a distance, even in genera like Dudres- 

 naya and Polyides, but that there is always a direct 

 transfer of cell-contents. The abstract question of 

 the nature of the sexuality in Florideae, as compared 

 with that of other orders, as Ascoraycetes and Col- 

 lemaceae, is treated at length; and he unites the 

 Bangiaoeae with Chlorophyceae, rather than with 

 Florideae, as has recently been done by Berthold. — 

 [Bericht. akad. loiss. Berlin.) w. G. F. [725 



Influence of sunny and shaded localities on 

 the development of foliage-leaves. — Stahl of 

 Jena has given considerable attention for several . 

 years to the effect which light has in the develop- 

 ment of the assimilative tissues. It has been held 

 by some that the degree of exposure of a leaf unfold- 

 ing from the bud can have no influence upon thfe 

 character of its cells, except so far as etiolation or 

 blanching might produce it. Upon reviewing all the 

 evidence in the light of his recent researches, Stahl 

 thinks that in shaded places the leaves have a less 

 well-marked palisade system, whereas in full sun- 

 light they develop a better palisade system and a less 

 well-characterized spongy parenchyma. The author 

 is convinced that these facts in i-egard to the partial 

 adaptation of leaves to their surroundings should be 

 borne in mind in the selection of the amount of light 

 in our greenhouses. The paper is well illustrated. 

 — {Zeitschr. naturwissensch., xvi. ; n. s., ix. 1, 2.) 

 G. L. G. 1726 



The largest flower. — Dr. Thurber gives an ac- 

 count of the pollination of EafHesia, written in an 

 interesting way for young readers. The immense 

 mottled flowers, with an expanse of three feet and a 

 weight of fifteen pounds each, are dioecious. They 

 are fertilized by flesh-flies, attracted by their carrion 

 odor. — (^mer. acrne., April.) w. t. [727 



ZOOLOGY. 



Structure and development of nematophores. 



— As the result of his study of the nematophores of 

 Aglaophenia, Antennularia, and Plumularia, Merej- 

 kowsky concludes that we must abandon the old view 

 that a nematoi)hore is an amoeboid mass of sarcode, 

 since the use of reagents shows that it is made up of 

 distinct nucleated cells. These cells are derived from 

 both layers of the body; the endoderm forming the 

 central axis, and the ectoderm the outer layer. The 

 nematophore is usually divided into two parts, of 

 which one shows no power of motion, and contains 

 a battery of very large lasso-cells ; while the second 

 portion is very movable, and exhibits amoeboid 

 changes of form. The active portiion is composed 

 entirely of ectoderm, while the immovable portion 

 contains an endodermal axis. The active portion pre- 

 sents a peculiar type of histological structure, since 

 its cells are embedded in and surrounded by a struc- 

 tureless layer of contractile protoplasm, which has in 

 itself the power of active change, and to the contrac- i 

 tile power of wliich the amoeboid movements are 

 due. This protoplasmic layer seems to correspond to 

 that which unites together the cells of labyrinthula; 

 and something similar is found in sponges. 



Merejkowsky's investigations of the development 

 of nematophores have led him to believe that these 

 structures are neither organs which have been ac- 

 quired for a special purpose, nor specialized polymor- 

 phic hydranths, but simply degenerated hydranths. 



In support of this view, he says, that, when a colony 

 of Plumularia halicioides was kept over night without 

 a supply of running water, the tentacles and oral ori- 

 fice disappeared, the whole body became reduced in 

 size, and the hydranth thus became converted into 

 something which bore a very close resemblance to a 

 nematophore. The ectoderm gave rise to long pseu- 

 dopodia, and changed its form continually, exhibit- 

 ing amoeboid movements which were almost exactly 

 like those of a true nematophore. — {Arch. zool. exp. 

 yen., 1882, 4.) w. k. b. [728 



Worms. 



Haplobranchus, a new serpulid. — A. Gr. Bourne 

 describes Haplobranchus aestuarinus, a new species 

 of serpulid, belonging, apparently, to the Sabellidae, 

 but differing from all known forms. A description, 

 including a few anatomical notes, is given. The worm 

 was found on both the Irish and English coasts. — 

 (Qitm-t jfrttrre. )?iic/-. sc, 188.3, 168.) c. s. ll. [729 



The species of branchiobdella on cray-fish. 

 — Oustroumoif has found a species near Kasan on 

 the gills of Astacus leptodactylus, but which is nearer 

 to B. parasita than to B. astaci, and for which he 

 proposes the name B. astaci leptodactyli. — {Zoul. 

 anz., vi. 76.) c. s. M. [730 



The teeth and synonymy of Dochmius. — 

 Megnin discusses the synonymy of the genera Doch- 

 mius, Strongylus, and Ankylostoma. Dujardin sep- 

 arated Dochmius as toothless forms: but Megnin 

 finds teeth in the Dochmius of the dog ; and, believing 

 that they will be foimd in the other members of the 

 genus, he maintains that the name ought to be re- 



