BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [34] 



With the Paguridae the alcohol must be changed often, and they are 

 to be preserved permanently in 90 per cent alcohol, because the shell is 

 permeable to only a small degree. 



The larvai of the Decapods {Zoea, Phyllosoma, etc.) are killed in sub- 

 limate or with a few drops of osmic acid of 1 per cent. 



PANTOP<lDA. 



The Pantopoda are killed in chromic acid of one half per cent so that 

 tLey will remain with the legs distended. As they are almost always 

 covered with foreign bodies, it is necessary to let them live for several 

 days in beakers of fresh sea water, so that they may. clear themselves 



of these extraneous growths. 



* 



MOLI^USCA. 



Lamellibranchs may be prepared with the valves open by narcotizing 

 them in alcoholized sea water, where they may remain from six to 

 twelve hours or even more, according to the species. The sii^honate 

 forms should not be transferred to alcohol before they are thoroughly 

 stupefied, otherwise the siphons will contract. After the animals have 

 been narcotized, it is an excellent plan to place them in chromic acid of 

 1 per cent for about a half hour. They are very likely to open their 

 shells wider after they have been placed in the chromic acid. When 

 chromic acid is not used, it is well to place a bit of wood between the 

 valves to keep them apart when first put into alcohol. Cocaine may be 

 used instead of alcoholized sea water for narcotizing the animals. The 

 animals are preserved in a more distended condition, but its use is not 

 as necessary for lamellibranchs as for gastropods, and the method will 

 be described when the latter are discussed. 



Lima, which has a large number of tentacular filaments around the 

 edge of the mantle, which break off' if alcoholized sea water be used, 

 is killed with chromic acid of one-fourth of 1 per cent. Large SjDecimens, 

 however, yield better results if treated with the copper sulphate solution 

 first. 



Scaphopoda. — Dentalium is narcotized with chloral hydrate of 0.2 of 1 

 per cent, in which it remains from ten to twelve hours or more, and is 

 then put into 70 per cent alcohol. 



Gastropoda. — The use of cocaine for narcotizing all species of gastro- 

 pods is strongly recommended. The solution consists of 2 grams of 

 cocaine powder dissolved in 100 c. c. of 50 per cent alcohol. Place the 

 animals in the least practicable amount of water. Drop in a few drops 

 of the cocaine solution, and after two hours add a few more, and con- 

 tinue the operation until the animals are thoroughly insensible. The 

 action is much slower in winter than in summer. To avoid the con- 

 traction into the shell, which is apt to take place with prosobranchs 

 having a spiral shell, even when the narcotizing has seemed to be 

 complete, "diaw the operculum as far out as possible with a pair of 

 pincers and bind it to the shell. 



