SPONGING. 459 



S. Lo BIANCO employs for the majority of Siphonophora a 

 mixture of 10 c.c. of saturated solution of corrosive sublimate 

 with 100 c.c. of 10 per cent, solution of copper sulphate. This 

 is used as in Bedot's process. Diphyes, Rhizophysa, and Phy- 

 salia, however, are killed with sublimate solutions ; Velella 

 with chromo-picric acid, or a mixture of 100 c.c. of sublimate 

 solution with 50 c.c. of 1 per cent, chromic acid ; Porpita by 

 poisoning with liquid of Kleinenberg. 



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 adminis- 

 tration of ether. 



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

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

 the most part extremely difficult to deal with on account of 

 the extraordinary delicacy of the tissues. S. Lo BIANCO em- 

 ploys for Callianira a mixture of I part 0'5 per cent, chromic 

 acid, 1 part concentrated pyroligneous acid, and 2 parts con- 

 centrated sublimate solution. For Beroe Forskalii he recom- 

 mends the cupric sulphate mixture, last section (I would point 

 out that the cupric sulphate method is very unsuitable for 

 many forms, as it makes them opaque, and so heavy that they 

 easily break). The majority of forms he treats with a mix- 

 ture of 100 parts of 1 per cent, chromic acid and 2 parts 1 per 

 cent, osmic acid, Cestus Veneris with chromo-acetic acid, 

 rolling it up like a watch-spring in order that it may not 

 become deformed by its own weight. 



SAMASSA has succeeded in making sections of Ctenophora 

 by means of the double-imbedding method, 306 (see Arch. 

 f. mik. Anat., xl, 1892, p. 157; Zeit. f. wiss. Mik., 1893, 

 p. 340). 



Porifera. 



856. Spongiae : Fixation. The smaller forms (Calcispongiae) 

 can be fairly well fixed by the usual reagents, osmic acid being 

 one of the best. For the larger forms no satisfactory fixing 

 agent has yet been discovered, so far as I can ascertain. 

 The tissues of this group are very watery, very delicate, very 

 friable after hardening, and macerate with the greatest 

 facility. For all but very small specimens, absolute alcohol 



