44, HOWARD AYRES. 
under a cover glass one is able to watch the slow removal 
of the calcareous substance in concentric layers. On such 
globules, after the acid has acted a short time, the structure 
called ‘reticulated calcareous tissue”’? by Lovén are seen as 
grooves on the surface of the globule or as knotches at the 
margin of the same (figs. 9, 18). The canals are often laid 
bare at one time for more than half the length of the globule. 
If the spheridia are treated with caustic soda to remove the 
animal tissues, the globules washed in water, then in alcohol, 
heated to drive out all traces of fluids, and then mounted in 
hard Canada balsam (not a solution in chloroform), which has 
been warmed sufficiently to allow the globule to sink into the 
balsam, but not so much that the balsam will enter the open 
canals, one has a preparation in which the canals instead of 
appearing as white lines, as they do in the living condition, 
or as water lines, as they do when simply dried, appear as 
black rods and lines of various sizes (figs. 5, 6, 7). This 
appearance is caused by the presence of air in the canals, 
which owing to the difference in the indices of refraction of 
the calcareous matter and balsam, on the one hand, and of the 
air on the other, hinders the rays of light entering the canals 
from reaching the observer’s eye. Again, if globules are 
treated as above and placed in a solution of safranine or 
hematoxylin after being placed in alcohol, and then removed 
from the colouring fluid to absolute alcohol and mounted in 
balsam the canals will be brought out as clear red or purple 
lines according to the staining fluid used (figs. 4, 10, 11). 
The colouring matter adheres to the walls of the canals, but 
does not stain the calcareous matter in the least. Further, if 
spheeridia are fixed to a slide by means of hard balsam, and 
their free ends or sides ground off, the canals will appear as 
grooves on the surface, or as circular or oval openings on the 
cut surface of the globule. 
I think it apparent from these experiments, which were 
acetic, osmo-chromic solutions, all of which produce essentially the same effect 
on the calcareous part of the globule. The acid should not be strong enough 
to cause an active effervescence. 
> eel 
