316 THE FOEAMINIFEEA 



Wallicli describes, it may be easily split from the 

 balsam when the latter is cold ; and, moreover, this 

 will provide a test as to the proper toughness of the 

 balsam, for it should shell off with ease when a knife 

 point is inserted under one corner, and it should 

 at the same time be noticed that the balsam does 

 not powder under the knife point, for in that case 

 it will be too brittle to grind with safety to the 

 shells. 



Some of the most interesting discoveries during 

 past years on the morphology of the foraminiferal 

 shell have been made by M. Schlumberger, and he 

 has shown by means of his superior skill in preparing 

 thin sections of Foraminifera, chiefly of the Milio- 

 lidae, that the same species presents two entirely 

 different aspects with regard to their inner plans of 

 growth, and to which reference has already been 

 made on the subject of dimorphism. The follow- 

 ing is a translation of Schlumberger's description 

 of his method of preparing these sections, which 

 is given by Heron-Allen in his useful and sug- 

 gestive ' Prolegomena towards the Study of the 

 Foraminifera : ' — 



' The apparatus necessary is very slight, and the 

 whole operation may be performed within the most 

 restricted space. A bottle of chloroform, one of 

 Canada balsam, a few stoppered tubes, two or three 

 fine brushes, a scalpel, a stone such as is used for 

 grinding razors, a piece of pumice stone, and a spirit 

 lamp are all that is necessary in addition to the 

 ordinary accessories of a good microscope. One side 



