NOTES AND MEMORANDA. 87 



It miglit be said to pass through conditions more nearly allied to 

 starch or to dextrine than to pure cellulose. Observations made on 

 P. sulfiireus and on several receptacles of Polypori, on Ptychogaster 

 albus, &c., have shown the frequency of the blue or red reaction of 

 iodine with fungine, contrary to what has been admitted hitherto. 

 The cause of this apparent contradiction doubtless consists in the 

 physiological phenomena here alluded to. It is worthy of remark 

 that the organs on which was first observed, as a sort of anomaly, 

 the blue reaction of iodine, belonged to the reproductive system, that 

 is to say, to the cellular elements of most recent formation. 



Polarizer for the Microscope. — At the meeting of the Physical 

 Society on 9th November, Professor W. Gr. Adams, the president, 

 explained a simple appliance made by Mr. S. C. Tisley for exhibiting 

 the coloured bands due to interference with thick plates. The bands 

 due to regular reflection and refraction were produced by two thick 

 plates nearly parallel to each other and fixed in a brass box with 

 rectangular apertures on its flat faces so that the light fell on the 

 first plate at an angle of 60°, the whole apparatus being of a con- 

 venient size for the w\aistcoat pocket. The elliptical interference 

 bands, due to the scattering or diffusion of light at a point on the 

 front sui'face of one of the plates, were shown by means of a precisely 

 analogous arrangement, except that the inclination of the plates to 

 each other was somewhat greater ; in this case the interference bands, 

 formed by regular reflection and refraction, fall in another direction, 

 so that they are not received by the eye ; the diffusion interference 

 fringes obtained were clearly visible when thrown on the screen. 

 They are formed by rays once diffused from points on the first surface 

 and afterwards regularly reflected and refracted from the froJit and 

 back faces of the two plates in succession. Professor Adams jjointed 

 out that this instrument would form a convenient means of obtaining 

 polarized light in cases where the length of a Nicol's prism is ob- 

 jectionable, for instance, under the stage of a Microscope ; the light 

 will be completely polarized if the plates be placed to receive the 

 light at the polarizing angle, and the field will be much brighter than 

 when a plate of tourmaline is employed.* 



New Anthozoa. — Professor Studer, of Berne, continues in the 

 July-August number of the ' Monatsbericht ' of the Berlin Academy 

 the description of the forms collected during the voyage of the 

 ' Gazelle ' round the world. 



The new species (all of which are figured) are the following : — 



Cereus brevicornis. 

 Calliactis rnarmorata. 

 Bunodes Kenjuelensis. 

 Bolocera Kerguelensis. 



Madrepora patella. 



,, selago. 



,, candelabrum. 



„ rubra. 



„ nana. 

 Seriatopora Jeschkei. 



„ cornpressa. 



„ contorta. 



Corynactis carnea. 



Actinopsis rosea. 

 Paractis alba. 

 Halcampa purpurea. 

 Edwardsia Kerguelensis. 



* ' Nature,' vol. xix. p. 6S. 



