VARIOUS INVEllTEBRATE ANIMALS. Ill 



When several specimens ai-e put into one bottle, each should be 

 tied np separately in rags. Large specimens may be preserved 

 dry, by immersing for two hours in fresh-water, followed by 

 immersion in ordinary alcohol for one day, and then by exposure 

 to sun and air. 



To preserve the delicate calcareous Ascon sponges so as to be 

 available for purposes of research, Professor Mincbin * takes Avith 

 him, on his collecting excursions, bottles containing 1 per cent, 

 osmic acid, distilled Avater, and picrocarmine solution. The sponge 

 is f)ut into a bottle containing equal parts of sea-water and 1 per 

 cent, osmic for from five to ten minutes. The specimen is rinsed 

 in fresh or distilled water, and placed in picrocarmine for from one 

 to two hours. Lastly, it is washed in distilled water, and transferred 

 to glycerine or alcohol. 



Hydrozoa. 



Hydroida (Sea-firs, etc.). — The more commonly known species 

 form branching treelike colonies rooted to stones, rocks, etc. 

 Shallow-water forms will be found in pools left by the tide ; 

 those from deeper water, often attached to stones or to the shells 

 of molluscs and similar objects, are obtained by dredging. 



The fresh-water forms Cordyloijliora and Hydra occur in rivers, 

 docks, etc. 



Specimens should be preserved in spiiit or in 10 per cent, 

 formalin. 



Moseley t recommended the following method for obtaining 

 specimens with expanded polyps : — Tlie living specimens are placed 

 in a tall jar, with just enough sea- water, well aerated by shaking, 

 to cover them. When the polyps are expanded, a hot saturated 

 solution of corrosive sublimate is poured in. In a few minutes 

 the sublimate solution is poured off, and fresh-water added, to be 

 followed by weak and then strong spirit. 



Specimens of the fresh-water Hydra should be looked for on 

 water plants. 



* "Quarterly Journal Microscopical Science," January, 1898, p. 474. 

 t H. N. Moseley, " Admiralty Manual of Scientific Enquiry," 5th edit. 

 Zooloijy, p. 857. 



