COLLECTING AND PRESERVING 313 



more difficulty. To show to advantage they should have 

 their tentacles exserted, and when there are retractile 

 branchiae, as in Doris, this should be extended. 



It is no easy matter to kill them in perfection as regards 

 these details. There is no royal road to this end. Some- 

 times suddenly plunging right off into strong spirit or a 

 hot solution of corrosive may achieve success, but what is 

 safer is to employ anaesthetics, as directed for zoophytes. 

 Formalin solution, ten per cent., will answer for most, 

 but Eolis, that parts readily with its leaflike processes, 

 although branches of its alimentary canal run into them, 

 is best preserved in seventy-five per cent, spirit. 



The Cephalopoda (Octopus, Sepia, etc.) are beautifully 

 preserved in the formalin solution, but Octopus, if killed 

 by plunging into the preservative, takes up a peculiarly 

 symmetrical form, the tentacles curled into flat spirals, 

 which is not natural. It is best not to put this one, at 

 least, into the preservative until it is dead. It can then be 

 arranged into proper form before the fluid is poured on. 

 An hour after it has been in the formalin it will be rigid, 

 and will retain the position in which it was arranged ; a 

 couple of changes, at intervals of a week, and they can be 

 finally sealed up for the museum. 



The Tunicates. These give varied results as regards 

 their appearance as museum specimens. The transparent, 

 pelagic forms, Salpa, Doliolum, etc., preserve very well by 

 simply immersing in formalin solution, or in spirits of wine 

 if it is brought to strength (sixty per cent, or seventy per 

 cent.) by degrees, but the beautifully coloured com- 

 pound forms, all the varieties of Botryllus, etc., lose their 

 colour entirely. A successful method of preserving them 

 has yet to be discovered. 



One species, however, may be to some extent preserved 

 with natural appearance ; this is the almost black 

 and white one (Botryllus mono). It will keep tolerably 



