1915] The Ottawa Naturalist. 103 



also allows one to quickly view detail on a surface one is grind- 

 ing down in order to reveal internal structure. 



The paleobotanist is well aware that soft parts may be pre- 

 served in fossil forms, for he not only recognises different tissues 

 but sometimes individual cells. For him there is a true paleo- 

 histology. The paleozoologist, on the other hand, has hitherto 

 been skeptical as to preservation of soft parts in fossil forms. 

 The marvellous finds of Wolcott, his beautifully preserved an- 

 nelida and delicate medusa-like holthurians — his reproductions 

 of inner organs and discovery of fossil crustacean livers which 

 still show their characteristic microscopic structure on cross sec- 

 tion — these things now compel the paleozoologist to also be- 

 come a believer. Traces of such soft parts should then be looked 

 for, and the gum mounting is peculiarly adapted to reveal 

 them. By this process-the author has been enabled (1913 (b) 

 plate IX, fig. 1) to show the remains of muscle fibres still adher- 

 ing to a well-defined muscle field lying between the right hand 

 fifth and sixth marginals of an arm of Protopaloeaster narrawayi. 



method. 



Portions of the crude gum are selected for their clearness 

 and lack of colour, and dissolved in benzol, to form a liquid 

 that will filter easily. The stock solution should be kept in a 

 glass-stoppered bottle, and a very fine bit of wire, or an insect 

 pin, kept between the stopper and neck of bottle. Portions 

 for use should be allowed to evaporate to such a consistency 

 that the fliiid will slowly drop from a glass rod. A regular drop- 

 ping bottle will be found to be a convenient receptacle for the 

 thicker gum. 



The specimen to be treated may be attached to a glass slide 

 by means of a few pellets of beeswax. Care should be taken to 

 have the specimen so oriented that when placed on the stage 

 of the microscope it will receive light at the angle which will 

 best emphasize the features to be observed. 



A cover glass of appropriate size and shape is then selected 

 and cleaned, the specimen freed from dust, and a drop of benzol 

 placed on it to free the pores or crevices from air. A few drops 

 of gum solution are now added, and a drop also placed on the 

 cover glass, which is then inverted and placed on the specimen. 

 Additional gurh may be easily run under the cover glass, and 

 if bubbles are present a slightly inclined position will allow them 

 to pass to one side and escape. Twenty-four hours or more is 

 usually required to so fix the cover glass that it will not creep 

 when placed on a vertical stage. 



In case the specimen has a small or convex surface, the 

 cover glass is first placed on a smaller support, such as the screw 



