ZOOLOGY AND BOTA.NY, MICROSCOPY, ETC. 1015 



bull's-eye stand. On the top of the upright there is a short horizontal arm, 

 to which the Microscope is attached. 



For portable and exhibition purposes the instrument fits on to the 

 Microscope lamp-stand, the same apparatus being used to attach it as in the 

 first case (fig. 238). 



When the Microscope is required for field or class purposes this attaching 

 piece is taken off", and is replaced by a handle (fig. 23'J). The handle and 

 the attaching piece are so arranged that the Microscope cannot shake loose 

 or twist off, or get off the square. 



When the instrument is used in the field, the mirror is swung to one 

 side, and the condenser is pointed to the sky. 



Woodhead's Microscope with large Stage. — This Microscope, devised 

 by Dr. Woodhead and made by Mr. H. Crouch, has a stage of unusually large 

 size, 11^ by 9f in., for the examination of sections through entire organs. 



Selenka's Electric Projection -Lamp for Microscopic Purposes.*— 

 Prof. E. Selenka describes a Projection-Microscope constructed for him 

 by Herreu Eeiniger, Gebbert, and Schall, of Erlangen, " which, by its 

 practical and convenient construction, fulfils its purpose in a remarkable 

 manner." He describes the apparatus fully " in the expectation that it will 

 soon be more largely used ; for thousands of microscopic objects can in this 

 way be used without difficulty for demonstration, and although there is no 

 question that the ordinary diagrams and lithographs have done, and will do 

 good service, yet the impression made by the exhibition of the object itself 

 is much more vivid and permanent than that produced by a representation." 



To show what objects are of value for demonstration in zoological 

 lectures, for a large circle of students, the author states that at a distance 

 of 5 metres from the screen the contractile vacuoles and the so-called 

 streaming of granules in living Amoebae are clearly visible, as are also 

 the ciliary movements and ingestion of food by Infusoria. " In stained 

 calcareous sponges the flagellated chambers and spicules may be shown, as 

 may also the cellular structure of the arms of hydroid polyps, and the entire 

 sexual apparatus in the proglottides of tape-worms. Trichinse, Echino- 

 rhynchi, Trematodes, worm-larvge, small Annelids mounted in balsam. 

 Rotatoria, and Copepoda in the living condition give incomparable images, 

 as also the larvae of Echinoderms and Molluscs. Sections of the embryos 

 of vertebrates stained with carmine or htematoxylin make excellent objects 

 to show the development of the vertebrae, heart, nerve-fibres, sense-organs, 

 amnion, allantois, and urogenital system. I can show without any 

 difficulty the cleavage of the egg, gastrulation, rudiments of the ccelom, 

 and even the formation of yolk-rays in the segmenting ovum, and the 

 filamentar loops in the dividing nucleus. Charming images are given by 

 the membrane between the digits of the foot of the living frog or the gills 

 of the Salamander larva, the tracheae of the flea or the louse, &c. And 

 how quickly and simply is the demonstration effected ! In those lectures 

 in which I intend to project microscopic objects, the discourse proceeds 

 without interruption, and the last five to ten minutes are used for the 

 demonstration. At a given signal the projection-lamp is put into action, 

 and then all that is required is the complete darkening of the auditorium. 

 This is rapidly and easily effected by lowering canvas blinds covered on 

 both sides with a thick coating of oil-paint of any desired colour. The 

 blinds are raised and lowered by means of a winch ; the demonstration is 

 made without any assistance. 



The light is obtained from a dynamo machine driven by an engine of 



* SB. Physikal.-Med. Soc. Erlangen, 1887, Heft 19, 8 pp. (1 fig.). 



