INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 147 



Mr. Wenham says,* that while he was never successful in the 

 patient manipulation required to bring out the striae of Anqjhipleura, 

 yet with the new illuminator he succeeded at once, and on every sub- 

 sequent occasion. This simple piece of glass, that looks something 

 like the half of a broken button, collects and concentrates a surjirising 

 amount of light, and is in a great measure a substitute for the costly 

 achromatic condenser, and can be used either in fluid contact with the 

 elide or not. 



The disk should be set in an independent rotating fitting, so that 

 if the object is turned by the rotation of the stage the disk may be 

 moved round to meet it, which movement also serves to modify or cut 

 off light. 



Powell and Lealand's Immersion Condenser. — Messrs. Powell 

 and Lealand exhibited, at the Scientific Evening on 3rd December, 

 their new immersion condenser. It is non-achromatic, and by means 

 of a large back lens an angle of light of about 130°, measured in 

 crown glass, can be utilized. Diaphragm slots are fitted beneath, by 

 which two beams of light at right angles can be used either together 

 or separately. The makers claim for it, that the most difficult known 

 test objects requiring oblique illumination can be resolved with the 

 mirror in the optic axis, the required obliquity of incidence being 

 produced by refraction through the condenser. 



Mr. Bolton's Tubes of Living Organisms.! — Mr. Bolton recom- 

 mends that as soon as the tubes (which are mostly ^ inch in diameter, 

 and 1^ inch long, holding ^ drachm of water) are received by post they 

 should be opened, uncorked, and, if they cannot be examined at once 

 in the Microscope, a hole should be bored by a cork borer in a bung 

 cork, and the tube passed into the hole so that the top is level with 

 the top of the cork, and the tube and its contents thus floated on the 

 surface of some water in a tumbler, basin, or still better, in an 

 aquarium. In this way much danger to the life of the more delicate 

 animal organisms will be avoided from variations of temperature, 

 which are not unlikely to occur in so small a body of water as the 

 tubes themselves contain. Many of the advantages of a large body of 

 water are thus obtained without any danger of the objects being lost, 

 or diffused over too large a field to be readily found again. 



In the examination of the tubes under the compound Microscope 

 they are awkward to fix, and the aberration of the light is so great 

 as to prevent the possibility of seeing anything with fair clear- 

 ness except through the centre of the tube. This difficulty may 

 be in great measure overcome by having a trough in which the tubes 

 will just lie diagonally. A tube being placed in such a trough filled 

 with filtered water, the aberration arising from its cylindrical fitrin is 

 appr(jximatcly counteracted, and it is surprising how easily its 

 contents can be examined to the very sides and bottom. 



As a diiqjing tube for the transfer of objects under the Microscope 

 he uses a sliDrt curved capillary glass tube, the upper end of which is 

 blown out into a little funnel, and the mouth covered with a piece of 

 stretched sheet indiarubbcr. A small orifice is pierced in the tube 



* ' Knglisb Mecliaiiic,' x\-x. (1879) p. HGO. t i^id., pp. 262, 288. 



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