i88 



HARDWICKE'S SCIENCE-GOSSIP. 



Motion in Diatoms. — On examining some 

 Spirogyra obtained from one of the fresh-water canals 

 to the east of Calcutta, my eye caught a diatom, 

 which in form resembled the figure of Bacillaria 

 paradoxa given in the Micrographic Dictionary. The 

 bacillaria is, however, described as a marine diatom ; 

 the water in the canal from which this specimen was 

 taken is fresh ; and the object was associated with 

 Spirogyra, a fresh-water conferva. The phenomenon 

 to which I would draw attention is the curious motion 

 of the frustules. Forming at the outset a raft (A in 

 the diagram, which is not a picture) composed of six 

 frustules, the outermost diatom on the left slid out 

 along its neighbour, which in its turn glided along 

 the third frustule of the series, and so on, until the 

 raft was arranged as at B B'. The diatoms then 

 slipped back to their first position, and as soon as it 



B C 



Fig. 126. — Diagram explanatory of movements of Diatoms. 



was attained, the outermost diatom on the right-hand 

 started off, to be followed by the whole series, until 

 the position C C was attained, when they slid back 

 to the first position B C, and then glided off to the 

 left, and so on, during the whole time the diatom was 

 under observation. This see-saw motion was kept up 

 with a regularity that suggested the working of the 

 shafts and rods of some well-regulated engine. I 

 notice in the pages of that exbaustless n ine, the 

 Micrographic Dictionary, that Thvvaites described 

 some strange motion in Bacillaria paradoxa. Did he 

 observe the same phenomenon I have attempted to 

 describe, or a different one ? My diagram is very 

 rough, the spaces between the frustules are exagger- 

 ated, for the diatoms were apparently in contact. I 

 could not notice any investing membrane, or gela- 

 tinous envelope, and I only hope I shall be able to 

 resume my acquaintance with the object. It was 

 very beautiful. — IV. J. Simmons, Calcutta. 



Helix aspera, var. sinistrorsa. — It will be 

 perhaps interesting to the readers of Science-Gossip 

 to hear, that I have lately found another reversed 

 Helix aspera near Bristol. It is a young specimen, 

 and will not attain maturity for two yea's. I intend 

 to carefully rear it. — Jessie Hele. 



ZOOLOGY. 



Conchological and Malacologicai. Notes. 

 — In Science-Gossip, 1885, p. 163, Mr. T. D. A. 

 Cockerell notices two varieties of Limax Jlavus 

 which I was fortunate enough to find near Middles- 

 borough. I refer to var. colubrina, Pini, and var. 

 virescens, Fer., and, as Mr. Cockerell seems to be 

 under some misapprehension with regard to the 

 latter, which is possibly due to my not having stated 

 the authorship of the variety, I hasten to make 

 amends. The variety virescens, Fer., is distinguish- 

 able by its greenish glassy appearance, with the usual 

 markings scarcely conspicuous. The original de- 

 scription runs : Limax virescens, maculis parum con- 

 spicuis. This does not agree with the variety vires- 

 cens of Moquin-Tandon, as quoted by Mr. Cockerell. 

 The specimen found by me agreed fairly well with 

 Ferussac's description, and I have since taken a highly 

 characteristic specimen in the same locality as the first. 

 With regard to the new variety of Helix ncmoralis 

 {Studeria, Moq.), which Mr. Cockerell proposes to 

 add to the British list, I may say that I have recently 

 been visiting on the borders of Wales, and near 

 Oswestry, Salop, have taken the variety which Mr. 

 Cockerell describes as lilac and bandless. This form 

 is moderately abundant in that locality, associated 

 with vars. Libellnla, Risso, Rubella, Moq., and 

 Castanea, Moq., into the latter of which it seems to 

 almost insensibly merge. My Oswestry shells are 

 at present in the hands of the Recorder of the Con- 

 chological Society, but on their return to me I shall 

 be happy to send Mr. Cockerell a specimen for com- 

 parison. Though the colour renders this shell a 

 beautiful cabinet object, yet I am loath to accord it 

 varietal rank — in fact, without expressing any decided 

 opinion, I am inclined to believe that the present 

 mode of making colour varieties is merely provisional, 

 as, so far as my experience goes, one colour merges 

 into another by such gentle grades that it is next to 

 impossible to say where one begins and the other 

 leaves off, and the student is lost when he seeks to 

 give place, in its rank, to his specimen. I am not, 

 however, prepared to suggest a way out of the 

 difficulty, unless we revert to the division proposed 

 by Sheppard, viz. 7/. ncmoralis, Shepp., the plain 

 unhanded form ; var. Cintra, Shepp., the one-banded, 

 or, according to the present system, 00300, and var. 

 fasciata, Shepp., the five-banded form. I do not, 

 however, agree with all his reasons for such separa- 

 tion, but rather because the many varieties of banding 

 and colour are readily referable to one or other of 

 these three. My own observation of H. ncmoralis 

 leads me to believe that the one-banded form breeds 

 most true, whilst the plain unhanded form generally 

 interbreeds with the other two. As to varieties 

 having such banding as the following, 10345, 02345, 

 I 00045, &c, I believe them all to be referable to 



