SCIENCE-GOSSIP. 



57 



Directory of Microscopists. — The editors of 

 "The Journal of Applied Microscopy" invite all 

 interested in biology, histology, pathology, petro- 

 graphy, and any persons engaged in microscopical 

 work, to express an opinion as to the advisability of 

 issuing, as far as possible, a complete directory of 

 microscopists in 1899. Such a directory would 

 furnish a ready means of communication between 

 the users of the microscope in various parts of 

 the world, so that exchanges of material and 

 experience might be effected. If Messrs. Bausch 

 and Lomb, of Rochester, N. Y., receive sufficient 

 encouragement it will be commenced forthwith. 

 We recommend the venture to the notice of our 

 readers. 



Holiday Microscopy. — By this time most of our 

 readers will have once again got their collecting- 

 bottles and nets into working order and will have 

 recommenced their studies of the microscopic life 

 of the ponds and ditches in the neighbourhood. 

 Nitella and Cham are now to be found in their full 

 vigour in pools and shady woods, and Spirogvra 

 and other freshwater algae are in full fruit in the 

 ditches and runlets. For the student of marine life 

 the sea grass Zostera marina affords an abundant 

 harvest of interesting parasitic species of algae on 

 its leaf-tips, and the Fuci and Laminarias present 

 many interesting object lessons in problems of 

 gfowth. In the shallow ditches by road-sides 

 diatoms flourish, and on the crests of the ripple- 

 marks left by the receding tide a rich harvest of 

 the Foraminifera may be gathered. 



Paraffin Imbedding Table. — Another form 

 of paraffin imbedding table recommended by 

 Mr. H. B. Ward in the same journal is made of a 



Paraffin Imbedding Table. 



triangle of sheet copper, with a base of six inches 

 and a perpendicular height of fourteen inches. 

 The edges of the triangle are turned under and 

 inward, giving to the table a smoothly rounded 

 margin. In height, the main part of the table 

 measures two inches, and it is four inches high 

 under the apex of the triangle, where is placed the 

 heating flame, which may be gas, or oil, or alcohol 

 lamp. 



Photo-micrography with High Powers. — In 

 "Nature" Messrs. J. E. Barnard and T. A. B. 

 Carver explain how they have overcome the 

 difficulty experienced in photo-micrography with 

 high powers and critical illumination, owing to the 

 unequal intensity of the light emitted from the 

 surface of incandescent limes, or the impossibility 

 of controlling the electric arc so as to maintain a 

 constant position and condition of the crater on 

 the positive carbon. The latter difficulty has now 

 been overcome by having a simple form of hand- 

 feed apparatus, with a pinhole camera attached, 

 through which an image of the carbon points is 

 projected on to a ground-glass screen. With such 

 a form of arc-lamp absolute " centration " of the 

 light can be secured and maintained, without 

 reference to the microscope, after the necessary 

 position of the image of the arc on the screen of 

 the pin-hole camera has been once obtained. 



The Ears of Worms and Ants. — Dr. J. Weir 

 has recently been carrying on some interesting in- 

 vestigations in connection with the ears of worms, 

 crustaceans and ants, and he has concluded from 

 these that many of the lower animals are capable 

 of hearing sounds whose vibrations are so many or 

 so few per second that the human ear is unable to 

 perceive them. He has demonstrated the fact that 

 ants can hear sounds that are produced by vibra- 

 tions exceeding 10,000 per second. The lowest 



Auditory Organs of Earth- 

 worm (Z.. ie;-yes^m). A, Audi- 

 tory organ ; b, noto chord. 



Tail OF Shrimp, e, Audi- 

 tory organs (after Lub- 

 bock). 



sound that the human ear can detect is produced, 

 probably, by about twelve vibrations per second. 

 He has extended his observations to the auditory 

 organs of worms, and in the " Scientific American " 

 he describes the modus operandi of his experiments. 

 If the third caudal segment of a common angle 

 worm be frozen and a thin section of its lower 

 surface be placed beneath a low-power lens, two 

 oval pinkish bodies lying immediately beneath can 

 be readily made out. When the section is staine i 

 with eosin, these little organs become quite visible 

 even to the naked eye. Two nerves start from 

 these bodies, one from each, and end in a ganglionic 

 enlargement of the noto chord or central nerve. 

 Reasoning by exclusion and analogy, and compar- 

 ing with the shrimp, whose ears are in its tail. 

 Dr. Weir concludes that these bodies are the 

 worm's organs of hearing. The ears of ants are 

 situate in their legs. If an ant's leg be examined, 



Tibia of Ant (L. flavus). 

 s s, Swellings of large trachea; x, chordotonal organ. 



a curious enlargement of its canal will be at once 

 observed. In the femur or thigh the diameter of 

 this canal is -^-^j^j^ of an inch, but when it enters the 

 tibia it swells to ^i^ of an inch. In the upper part 

 there is a conical striated organ which bears some 

 resemblance to the organ of corti in the human 

 ear. This constitutes the auditory organ of the 

 ant. Dr. Weir's paper is most suggestive and 

 instructive, and it contains in some detail descrip- 

 tions of the various experiments upon which his 

 conclusions are based. 



