28 



THE AMERICAN MONTHLY 



[February, 



I 



such small bladder-like cells, as a 

 new species of Oocys/is, if its further 

 development did not show that we 

 have to deal here with one of the 

 forms of Glceocystis vesiculosa. 

 {To be continued?) 



The Preparation and Mounting 

 of Objects. 



V. A few special methods were 

 promised for this number of the 

 Journal. The first one to be mention- 

 ed is Stodder's method of mounting 

 diatoms. This method is sometimes 

 useful when rather large diatoms are 

 to be mounted in situ, in balsam. Dia- 

 toms mounted in this way sometimes 

 form very beautiful objects for the 

 paraboloid illumination. It is neces- 

 sary to remove all the air from within 

 the valves, and as this is sometimes 

 a difficult matter, Stodder's method 

 is a very good one. 



The diatoms, attached to the bit of 

 sea-weed or other object, are thor- 

 oughly dried, and immersed for a 

 short time in chloroform. They are 

 then transferred to the slide and a 

 few drops of balsam dissolved in 

 chloroform are quickly added. As 

 the chloroform evaporates from the 

 frustules, the balsam-solution takes 

 its place, so that the diatoms are all 

 filled with balsam and free from air- 

 bubbles, while the appearance of the 

 sea-weed is not injuriously affected. 

 Benzole and benzole-balsam will act 

 equally well. With such frustules as 

 the Jsthmia, we have made some beau- 

 tiful slides in this manner. 



Mr. C. C. Merriman's method of 

 mounting Foraminifera gives very 

 fine results with some shells, particu- 

 lary with flat ones like Peneropolis, 

 Orbiculina, etc. The shells are care- 

 fully selected and immersed in spirits 

 of turpentine. They are then transfer- 

 red to a drop of balsam on a cover- 

 glass, tastefully arranged, and the 

 balsam is then thoroughly hardened 

 by heat. When the balsam is hard it 

 is coated with asphalt, and this also 



is allowed to dry thoroughly. The 

 cover-glass is then mounted on the 

 slide. We thus make an opaque bal- 

 sam-mount and the white shells show 

 very well against the black ground of J^ 

 the asphalt. \^ 



Polycystina may be mounted as 

 transparent objects in balsam, but 

 very beautiful slides can be made in 

 another way. The glassy appearance 

 of the Polycystina makes them in- 

 ferior objects when mounted dry in 

 opaque cells, but if they are heated 

 on platinum-foil, mica, or on some 

 other support, either by means of a 

 blow-pipe flame or over a lamp, they 

 lose their glassy appearance and be- 

 come opalescent. They are then very 

 beautiful objects for opaque mounting. 



Polyzoa and Zoophytes are always 

 interesting objects if properly pre- 

 pared. The encrusting Polyzoa would 

 naturally be mounted as opaque ob- 

 jects but the plant-like forms may 

 sometimes be mounted in balsam, or 

 even dry, for transmitted light. When 

 they are mounted as opaque objects 

 they usually require but little clean- 

 ing, but for transparent objects it is 

 desirable to remove the contents of 

 the cells. It is to be understood that 

 we are writing about the dried speci- 

 mens, not of the living animals. The 

 usual method of cleaning the poly- 

 pidoms is by the use of the air pump, 

 but we have succeeded very well 

 without it in this manner: First boil 

 the objects in a test-tube in water, to 

 remove the air from the cells ; then 

 soak them in a saturated solution of 

 washing soda (carbonate of soda), 

 and then pick them out of this solu- 

 tion with forceps and dip them into 

 dilute hydrochloric, or some other 

 acid. The rapid evolution of gas 

 that ensues drives out the contents 

 of the cells, and often cleans them 

 perfectly. They should then be pre- 

 served in alcohol, or in camphor-water. 

 Another process for removing organic 

 remains, is to place the objects in 

 Avater and allow decomposition to 

 take place. 



o 



