HARDWICKE'S SCIENCE-GOSSIP. 



1S3 



tions are consequently but slow, and without the 



mesmeric power they would have some difficulty 



in procuring the food requisite for their sustenance. 



Blachheath. Henky A. Auld. 



MICROSCOPY. 



Self-dia^ioION of Diatoms. — Professor Smith, 

 speaking of the subject of self-division of the 

 diatoms in the Lens, remarks : — " It may be ob- 

 jected that if by self-division the frustules become 

 smaller, then the persistent filamentous forms, at 

 least some of them, should, upon measurement, 

 actually exhibit this gradation in size. I reply that 

 this is the case, and in a filament of thirty-seven 

 double frustules of a large Melosira moniliformis, 

 I find the middle frustules larger by °0001" (with 

 the one-eighth objective, thirty divisions of my 

 Powell and Leland thread micrometer), and so re- 

 peatedly of other chains of frustules. It would 

 not at first appear that the largest frustules should 

 be at the ends, and not the middle of a filament. 

 We must remember, however, that although the 

 two larger primary valves may be carried to the 

 ends if the filament remains unbroken, yet all the 

 time self-division is occurring between ; so that a 

 series of nodes or swellings will exist all along the 

 chain. Eor example, if after the formation of, say, 

 half a dozen frustules, so nearly the same size that 

 we may consider them equal, we now suppose self- 

 division to occur simultaneously, so that each 

 frustule produces six others ; then these latter, 

 smaller than the older ones, would be distributed 

 throughout the chain, and these again, all simul- 

 taneously dividing, would give rise to still smaller 

 ones interposed; and it is manifest that a chain 

 would very likely be severed at the smaller frus- 

 tules, and the partial filaments would have the 

 larger and older (perhaps thus more siliceous) 

 frustules, near the middle, unless we should chance 

 to find one of the ends with the valve of the 

 primary frustule, which would rarely happen." 



Crystals of the Willow. — Can any of the 

 readers of Science-Gossip tell me a good method 

 of obtaining salicine crystals from the willow as 

 microscopic objects ? — C. E. B. 



CoLOUEED Light.— Can any of your readers kindly 

 give me the reason of the following phenomenon ? I 

 have a slide of leopard's hair mounted in balsam, 

 and on being placed under the microscope, out of 

 focus, two or three of the hairs appear coloured — 

 orange down the centre of the hair and blue at the 

 edge. On adjusting the focus properly, the colour 

 entirely disappears. What is the cause of only one 

 or two being coloured like this ? I may mention 

 that the microscope I use is an achromatic com- 



pound one, and the light that of an ordinary candle. 

 — Ernest G. Spiers. 



Circulation of Blood in a Frog. — It may be 

 interesting to some of the readers of the Science- 

 Gossip, who have never seen the circulation of 

 blood in any animal, to experiment on a frog. 

 When a frog is caught, tie up its head, body, and 

 three of its legs in a bag, leaving one of its hind legs 

 hanging out. Then put the latter under the mi- 

 croscope, and the circulation will at once be seen 

 going on. When the experiment is finished, the 

 frog may be let go, none the worse for the examin- 

 ation it has undergone. — /. L. J. 



New British Alg/E.— Mr. E. M. Holmes has 

 described two new species of British Alga; in 

 Grevillea for July, under the names of Calli . 

 thamnion Iiormocarpiim, and Nitophylluin thysano- 

 rhizans. The former has capillary fronds densely 

 tufted, one to two inches high, and of a pinkish- 

 purple colour. Both species are from the neigh- 

 bourhood of Plymouth. 



ZOOLOGY. 



New Natural History Society. — We are glad 

 to notice the formation of a new Natural History 

 Society at Whitchurch, in Shropshire. The first 

 meeting was held in June, when the President, the 

 Bev. W. H. Egerton, enlarged on the claims which 

 natural history questions had on all intelligent 

 people. The connnittee and secretaries appear to 

 be very energetically pushing forward the society, 

 which is certainly well situated, both geologically 

 and botanically. 



The Young of the Batrachia.— It is weli 

 known that most of the batrachia are hatched in 

 a form very diiferent from that which they ulti- 

 mately assume, the young animals living in the 

 water in the form of tadpoles. A few species, how- 

 ever, furnish exceptions to this rule, such as the 

 Surinam toad, in which the young are developed 

 in little pits in the back of the female, and an 

 American frog, the female of which has a regular 

 pouch under the skin of her back, in which the eggs 

 are retained until the young animals are sufficiently 

 developed to hop about and seek their own living- 

 M. A. Bavay has brought to our knowledge another 

 exception to the general character of the Batra- 

 chiau group. A tree frog (llylocles martinicensis) is 

 abundant in Guadaloupe, an island formed almost 

 entirely of volcanic rocks, and on which fresh water 

 exists only iu the form of streams so violent as to 

 render the existence of such creatures as tadpoles 

 almost an impossibility. M. Bavay's attention was 

 thus called to the development of the frog, and he 

 has found that it passes through its tadpole stage. 



