have been made by a treatment with a saturated solution of 

 corroxive sublimate. 



Sphaerozoidae. — The different species of the genera 

 Sphaerozoum and Collozoum, which have spherical or cylindrical 

 form, are fixed in iodinized alcohol of 35 per cent, where they 

 should remain from fifteen minutes to about an hour. The vessel 

 containing them should be shaken from time to time, because the 

 animals flatten out if they are allowed to remain too long on 

 the bottom. If it is desired to prepare a large number at one 

 time, it is necessary to put the fixing liquid into a crystal- 

 lizing dish of ample size, for convenience in manipulation. 

 After a sufficient time they are transferred to alcohol of 35 

 per cent, where they can remain a few hours. The change is 

 effected by transporting the colonies with a spatula to another 

 crystallizing dish of the same size without allowing the animals 

 to be without liquid. In the same manner they are transferred 

 to alcohol of 50 per cent, and after twelve hours to that of 70 

 per cent, and the last should be renewed after twenty-four 

 hours. In this manner colorless preparations are obtained which 

 can also serve for histological studies. Osmic acid is not 

 recommended, because it darkens the preparations too much. 



In colonies of Sphaerozoum with isosporic structure 

 the shape is not fixed with iodinized alcohol, and it is necessary 

 to use saturated sublimate. The genera Myxosphaera, Acrosphaera, 

 and Collosphaera are killed in chromic acid of 1 per cent, to 

 which a few drops of osmic acid have been added, using the same 

 form of receptacle and the same precautions mentioned under 

 Collozoum. After from half an hour to an hour the acid solution 

 should be poured off and fresh water substituted for washing, 

 but great care must be exercised not to break the colonies. 

 Then the objects are gradually transferred to alcohol. 



Acinetidae. — Trichophrya salparum has yielded beautiful 

 microscopical preparations when treated with concentrated sub- 

 limate in sea water. With Acineta foetida, which usually lives 

 among hydroids, better results can be obtained with osmic acid. 



Vorticellidae. — The colonies of Zoothamnium are best killed 

 with boiling saturated sublimate. 



Porifera 



For sponges which are to be used for exhibition, it is 



These methods are described in full by K. Brandt on pp. 7-11 

 of his monograph: Die Koloniebildenden Radiolarien (Sphaerozoien) 

 des Golfes von Neapel, in Fauna Flora Golf Neapel, XIII, Mono- 

 graph, 1885. 



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