1894.] MICROSCOPICAL JOURNAL. 37 



chamber moist. The chamber is now ready for immedi- 

 ate microscropic examination under a low power, e.g. 30C 

 diam. The object is to find and mark such cells as are 

 laying in the gelatine separate from other cells. Con- 

 sequently every plot on the cover is carefully searched. 

 Beginners should take care to focus down first, so that 

 the cover is in focus, and then go slowly further until the 

 gelatine layer covering the under surface of the cover is 

 reached. Here isolated cells are to be searched for. It 

 is well to draw a big square in the note book, divide it 

 into sixteen squares and draw the figures of the numbers 

 just as they appear in the field of the microscope. In 

 the respective places in the small squares in the note 

 book, the isolated cells are then marked as they appear 

 in the gelatine layer perpendicularly under the squares 

 engraved on the cover glass of the chamber. Whenever 

 a cell has been noticed, its surroundings in the gelatine 

 are carefully searched and the following points strictly 

 followed : 



(a). The whole gelatine layer must be searched, not 

 only the part which is in focus. Healthy looking cells 

 are marked in the note book with an o. 



(b). Two cells situated close together, at the side or 

 above each other, are noted oo or 8 according to their 

 position, but although their growth is watched, they are 

 not used afterwards. 



(c). Two cells within the same limits of the field are 

 not used, but must be marked o-o. 



(d). Dead cells or apparently dead gells are marked x. 

 They are also watched in the course of the development. 



When every field or plot has been examined, or when 

 25-30 cells conveniently situated have been marked, the 

 moist chamber is placed beneath a bell glass and put 

 aside. It must not be placed by 25°C. in the thermostat, 

 but kept below 20°C., as the gelatine becomes liquified 

 by a temperature a little above 22°C. The marked cells 



