526 Transactions of the Society. 



consider Bouin's picro-formol solution, of which I have abeady 

 given the formula, heads the list. It is a splendid fixative, has 

 great power of penetration, and kills very quickly. Material fixed 

 in this fluid is easy of treatment and stains sharply and clearly, 

 which is of immense importance not only histologically, but if 

 accurate photomicrographs are to be obtained. Fixatives contain- 

 ing chromic acid or bichromate salts should not be used, as the 

 material treated in such solutions is always difficult to stain, does 

 not stain sharply, and will often, though visually fairly satisfactory, 

 yield anything but good photomicrographs. Personally, I consider 

 the two best and most useful fixing fluids for general marine 

 biological work are Bouin's picro-formol solution, and the simple 

 saturated solution of corrosive sublimate (bichloride of mercury) ; 

 the latter, however, must be very thoroughly washed out to obtain 

 the best and sharpest staining. One drawback to the use of the 

 corrosive sublimate solution is that if added to the fluid containing 

 cocaine, a white precipitate will be thrown down on the specimens. 

 This precipitate can, however, be redissolved by washing the 

 specimen in one or two changes of alcohol. 



Hydrochloride of cocaine I consider, after long experimenting, 

 to be probably the best ansesthetic for a whole host of the smaller 

 forms of marine life, while menthol comes second, and is par- 

 ticularly valuable for larger marine animals. Alcohol of about 

 70 p.c. is a useful narcotic in many cases, and I have frequently 

 used it successfully for Hydroids when out of a supply of cocaine. 

 It must be added very slowly drop by drop, however, and the 

 specimen kept under careful observation, as its effect on different 

 subjects varies considerably. With patience and watchfulness it 

 may be employed with considerable suceess. 



Solutions of cocaine do not keep for long, fungoid growths 

 frequently appearing in the fluid after the lapse of a short time. 

 It is advisable, therefore, only to make up small quantities at a 

 time, just sufficient for the work in hand. 



For general purposes weak osmic acid is one of the best 

 solutions for preserving marine Protozoa. To the water containing 

 them I add a few drops of a ^ p.c. solution of osmic acid. The 

 organisms are then allowed to settle, or may be separated by 

 means of a centrifuge. They are then stained with dilute picro- 

 carmine, and passed through increasing strengths of alcohol. 

 Many of the Radiolaria are best preserved with corrosive sublimate, 

 Acanthometra giving particularly good results. Species of 

 Sphserozoa may be fixed with equal parts of 70 p.c. alcohol and 

 sea-water, with the addition of a little tincture of iodine, or with 

 a 5-15 p.c. solution of corrosive sublimate in sea-water. I have 

 also used Fol's method with some success in dealing with delicate 

 marine Infusoria. To the water containing the organisms a small 

 quantity of a perchloride of iron solution, composed of 1 vol. of 



