[15] THE PEEKERVATION OF MARINE ANIMALS HOVEt. 



Sphcerozoidce.^ — The different species of the genera Sphcerozoum and 

 Collozoum, which have spherical or cylindrical form, are fixed in iodin- 

 ized alcohol of 35 per cent, where they should remain from fifteen min- 

 utes 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 recom- 

 mended, because it darkens the jjreparations too much. 



In colonies of Sphcerozoum with isosporic structure the shape is not 

 fixed with iodinized alcohol, and it is necessary to use saturated subli- 

 mate. The genera Myxosphcera, Acrosphwra, and Collosphcera 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 precau- 

 tions mentioned under Collozouyn. 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. 



Acinetidce. — Trichophrya salparum has yielded beautiful microscopi- 

 cal preparations when treated with concentrated sublimate in sea 

 water. With Acineta fcetida, which usually lives among hydroids, bet- 

 ter results can be obtained with osmic acid. 



Vorticellidce. — The colonies of Zoothmnnium are best killed with boil- 

 ing saturated sublimate. 



PORIFERA. 



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

 immerse them directly in 70 j^er cent alcohol, renewing it when it 

 becomes discolored. To avoid the contraction of Halisarcidse, they 

 should be fixed in chromic acid of i per cent for about half an hour, 

 or in saturated sublimate for fifteen minutes. Those sponges which 

 are to serve for study, if they are not too large — that is, if they are not 

 more than 10 cm. (4 inches) in diameter — are immersed in 90 per cent 

 alcohol or in absolute alcohol, which should be renewed after three or 

 four hours, and again after twenty-four to forty-eight hours. If the 



^These methods are described in full by K. Brandt on pp. 7-11 of his monograph : 

 Die Koloniebildenden Radiolarien (Sphserozoien) des Golfes von Neapel, in Fauna 

 Flora Golf Neapel, XIII, Monograph, 1885, 



