45 
on a cord stretched across the room. Some trouble having been expe- 
rienced in keeping the moth from crawling out of the cell at either side 
of the pin, which is the method of closing it shown in the cut, the 
scheme shown in Fig. 26 was adopted last year in the Department. 
Fic. 26.—Method of clamping cells (original). 
This consists in clamping the bags in fours between two sticks of wood, 
rough sawn, about one-half by one-quarter inch through and 14 inches 
long. They are bound together by rubber bands and may be laid 
across parallel wires stretched across the room at about 13 inches apart. 
M. Pasteur suggests that a simple piece ef cloth about four inches square 
be used instead of the sack. The moth lays her eggs on this and is then 
retained by being fastened to the cloth, the corner of which is turned 
up over her and a pin passed through it and over her wings (Fig. 27). 
Fic. 27.—Cell used in the Pasteur system of egg-laying (after Pasteur). 
Some trouble has been experienced by this process, as the eggs, if not 
properly gummed to the cloth, will sometimes fall off and be lost, and 
the moths, not being confined as in the sacks, will wander to other 
cloths and get their eggs mixed with those of other moths, which would 
be detrimental to the microscopical selection to be hereafter described: 
It has the advantage, however, of enabling the microscopist to avoid 
the labor of turning the sacks. 
