726 Scientific Proceedings, Royal Dublin Society. 
but does not make the specimens brittle, so that they could be cut 
easily without injuring the septa. For microscopic work, one of — 
the specimens hardened in formaldehyde was also used; it had 
been in the reagent for some weeks, having been fixed in five per 
cent., and transferred in a few days toa four per cent. solution; it 
was stained in borax carmine, dehydrated with absolute alcohol, and 
imbedded in paraffin ; this specimen shows the histological details 
very well, though the ectoderm was not stained as deeply as usual ; 
the cilia were very distinct. It does not seem to have suffered from 
dehydration in any way, and the cells are not much vacuolated.* 
One large specimen was fixed and hardened in a mixture of 
three and a-half per cent. each of bichromate of potash and 
formaldehyde (this mixture keeps badly) as a fixing reagent; it 
acts slowly and does not cause very complete contraction. Asa 
hardening reagent for general use, specimens may be left in it for 
from ten daysto a fortnight, and a much longer time may beallowed 
to elapse without overhardening; the fluid must, of course, be 
changed from time to time. This specimen was cut up into four, 
and after three days two parts were transferred to nitrate of silver 
seventy-five per cent. solution, to try if Golgi’s reaction could 
be obtained. These were afterwards dehydrated with alcohol 
imbedded in paraffin, and cut; but the chromate of silver had only 
formed a coating on the outside, though the tissues were in a 
good state of preservation. Carlgren (1893) also failed to stain 
Actinia after Golgi’s method. The two other pieces which had 
been hardened for about a fortnight in bichromate and formal- 
dehyde were washed in water for twenty-four hours, stained in 
borax carmine, dehydrated for several days in alcohol (in the 
dark), imbedded in paraffin, and cut—one part longitudinally, the 
other transversely ; this method of hardening is admirable for the 
histological details; the cilia are unusually well seen (perhaps this. 
is due to the formaldehyde as they are very distinct also in the 
sections hardened in it). Some specimens were also stained with 
methylene blue, the living or recently killed animals being put 
into a solution of ‘75 per cent. sodium chloride and methylene 
blue, and left for twenty-four hours; the specimens were then 
1 Some other specimens hardened in formaldehyde did not stain well. I believe 
prolonged after-treatment with alcohol is advisable to ensure uniform results with 
formaldehyde material. 
