CTENOPHOEA. 375 



teasing with needles. A camel-hair pencil also sometimes 

 renders good service. 



747. Siphonophora. This group contains some of the most 

 difficult forms to preserve that are to be found in the whole 

 range of the animal kingdom. You have not only to deal 

 with the very great contractility of the zooids, but with the 

 tendency to general disarticulation of the swimming-bells and 

 prehensile polyps. 



The recent method of BEDOT has been given in 44A. 

 Bedot states that the most important point in this process is 

 the bringing into alcohol of gradually increased strength. 

 The liquid of Flemming for hardening ought to be added to 

 the solution of sulphate containing the Siphonophore, and 

 about two volumes of it should be taken for one of the sul- 

 phate solution. After hardening in the mixture a few drops 

 of 25 per cent, alcohol should be added to the fluid, with a 

 pipette, being dropped in as far as possible from the colony, 

 which should be disturbed as little as possible ; and further 

 alcohol of gradually increasing strength should be added so 

 gradually that the strength of 70 per cent, be not attained 

 under fifteen days at least. 90 per cent, alcohol should be 

 used for definitive preservation. 



KOROTNEFF'S method of paralysing with chloroform has been 

 given in 11. I would only add that I have seen Physophora 

 very successfully killed by the careful administration of ether. 



748. Ctenophora : Fixation. The small forms are very easily 

 prepared by means of osmic acid. The large forms are for 

 the most part difficult to deal with on account or the extreme 

 delicacy of the tissues. I suppose nobody has ever success- 

 fully prepared a large Eucharis. DE CASTELLARNAU recom- 

 mends fixing in a mixture of 200 c.c. of 1 per cent, chromic 

 acid with four to five drops of 1 per cent, osmic acid. 

 According to GARBINI (Mariuale, p. 154) SALVATORE LO BIANCO 

 employs for Callianira a mixture of " 1 part chromic acid, 1 

 part pyroligneous acid, and 2 parts sublimate/' but, unfortu- 

 nately, Garbini does not give the strength of the solutions. 



