THE VALUE OF FORMALIN. 57 



therein. The small medusae, Sarsia, &c, are also a great success 

 when treated in the same way. Here, where the objects are of great 

 delicacy, I wish to emphasize the importance of making up the 

 Formalin solution with sea-water. The observance of this precaution 

 in some cases is absolutely necessary. With large and stout animals, as 

 fish, molluscs and the like, a fresh water solution is, however, per- 

 fectly admissible. 



ACTINOZOA preserve well also, but though the new treatment 

 has its advantages in transparency, I hesitate to say that it is better 

 for museum purposes than well prepared spirit specimens, as alcohol 

 imparts a very useful stiffness to the tentacles that is somewhat 

 lacking in the formalin ones. Much depends upon the dangers of 

 transit ; thus where specimens can be prepared on the spot and 

 deposited on the museum shelves without a railway journey, then I 

 would recommend the formalin preparation made with a 6 °/ or 7 °/ 

 solution, but if this cannot be done on the spot, then spirit specimens 

 will probably stand a railway journey better. For dissection purposes, 

 formalin is, however, fully equal, and in some cases decidedly 

 superior. 



ECHINODERMS. Here I incline to prefer spirit to formalin 

 though both are good. 



VERMES. The same remark applies here as in the preceding case. 

 There is really little to choose between the two methods. 



CRUSTACEA. For the smaller, such as Copepods, Amphipods, 

 &c, formalin is very useful when the objects are not required to be 

 mounted to show internal anatomy. Especially good is it for those 

 doing tow-netting, &c, at a distance from a laboratory base, where 

 all facilities are at hand. In such cases all that is requisite is to kill 

 the organisms either by the application of an ordinary fixative or by 

 pouring in a little strong formalin to cause the animals to settle to 

 the bottom of the vessel, so allowing the superfluous water to be 

 poured off ; this done, all that remains is to bottle the remainder in a 

 strong solution — I prefer an 8 "/„ strength — label and put away. 



For the larger specimens it also does well if used strong ; if used 

 at all weak, there is a tendency for the carapace to rise, leaving an 

 unnatural space between the hinder edge, and the anterior edge of 

 the succeeding segment. I notice, too, that limbs tend to become 

 more brittle than in the case of spirit specimens, while the fluid 

 frequently becomes milky, due, I believe, to chemical action on the 

 lime set up by some acid product of the formalin solution. Hence 

 it is inadvisable to use this fluid for museum preparations when 

 much caleareous matter is present. 



MOLLUSCA gives most excellent results by formalin, and are 

 superior in appearance, and in dissection qualities, to spirit ones. 

 1 cannot award too high praise to formalin for use upon these 

 animals. 



TUNICATA. The same praise applies equally here, especially in 



