352 



DWIGHT E. MINNICH 



formed allowed free access to the interior of the cylinder. In 

 one_of them a small opening (fig. 2, o), 3 by 4 cm., was cut for 

 purposes of observation. 



The top of the cylinder was similar in construction to the side 

 walls except that the cardboard layer was omitted. Near oppo- 

 siteedges of the top, two circular openings, 8 cm. in diameter, 



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^ 



Fig. 2 Diagrammatic section through non-directive light apparatus, c, 

 transferring cage; e, entrance to light chamber; h, handle of slide opening and 

 closing e; o, opening for observation; s, light screen; v, ventilators. 



were cut (fig. 2, v). These were covered with a thin, white gauze 

 of coarse mesh, and served as ventilators, preventing any undue 

 rise of temperature within the apparatus. The bottom of the 

 cylinder was formed by a layer of heavy, dead white paper, which 

 covered the table on which the cylinder stood. This paper was 

 especially selected to afford a good creeping surface. On it was 

 drawn a plan, similar to that shown in figure 3, by means of which 

 the course of a creeping bee could be accurately followed. 



