roR zoor.or.icAi. itrtosks. 



bellows the bell-jar is filled with the dense fumes of the tobacco, and 

 the whole apparatus is left for some hours. Then the fumigation is 

 repeated in the evening, and the next morning an open bottle con- 

 taining a little chloroform is placed under the bell-jar and left there 

 for two or three hours. After this the anemone is usually found to 

 have lost its irritability, and not to contract or move when touched, 

 and it is finally killed and fixed in the expanded condition by a 

 mixture of chromic acid (i per cent.) ten parts, pure acetic acid loo 

 parts. It is left in this only a few seconds, and is then transferred to 

 chromic acid ^ per cent, for a few hours, and then to alcohol. This 

 method would probably succeed well with Tealia crassicoriiis. 



Hydromedusae. — The fixed branching compound forms of the 

 Hydrozoa such as Ohelia, Sertularia^ Tubularia, etc., can all be fixed 

 with little difficulty by pouring suddenly over them hot concentrated 

 sublimate solution when they are fully expanded in a small quantity 

 of sea water. They must then be emptied out into cold water and 

 washed for some time in a gentle current of the same, and then be 

 transferred to alcohol of increasing strengths. The small delicate 

 Medus.^, which are derived from the fixed hydroids, are killed in 

 various ways. Many can be well fixed with a mixture of sublimate, 

 saturated solution, and acetic acid, in the proportion of two parts of the 

 former to one of the latter. Others are killed with acetic acid pure, 

 and then transferred to a mixture of alcohol and chromic acid equal 

 parts, in which they remain for fifteen minutes, after which they 

 undergo the usual treatment with alcohol. 



Another reagent very useful for MedusiE is chrom-osmic acid 

 made by mixing together chromic acid (i per cent, solution) loo 

 parts, and osmic acid (i per cent.) two parts. Our common Aure/ia, 

 often occurring in summer in hundreds and thousands, is prepared 

 by placing it in this mixture for about an hour, then rinsing it in 

 fresh water and transferring it to weak alcohol. To avoid the flat- 

 tening of the medusa it may be placed when in the alcohol, um- 

 brella downwards, in a concave clock glass, or suspended in a loose 

 muslin bag. Rhizostoma and other large medusae may be prepared 

 in the same way, or may be killed in a mixture of three parts of 

 osmic acid (i per cent.) to loo of sea water. Specimens should 

 only be left in the osmic until they have acquired a light brownish 

 tinge, then washed in fresh water and transferred to weak alcohol. 



Ctenophora. — Only Horiniphora plumosa (often called Pleuro- 

 hrachia) and l^eroe ovata occur commonly nn the British coast. The 



K 2 



