ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 805 



and holding tlie split open by a knife-blade, place the severed head 

 in the cleft with the top downward, and, withdrawing the knife-blade, 

 allow the stick to close upon the head, when it will fully distend the 

 tongue. Now dip the head and tongue in turpentine and leave it 

 immersed for a few days, when it will be found well cleaned, still 

 perfectly distended, and can be released from the stick or cut from 

 the head without danger of its collapsing. Mounted in a cell in 

 balsam, it is a truly beautiful object. 



Perchloride of Iron as a reagent for Preserving Delicate 

 Marine Animals. — We have already referred (vol. iii. (1883) p. 729) 

 to Dr. H. Fol's objection that the reagents in common use for instan- 

 taneous killing, such as picro-sulphuric acid, osmic acid alone or in 

 combination with chromic and acetic acid, and eorrosive sublimate, 

 fail to give successful preparations, and noted his success with per- 

 chloride of iron. He now adds some further remarks on the subject.* 



An alcoholic solution diluted to about 2 per cent, will answer 

 ordinary purposes, but a stronger solution should be used in case it 

 is desired to kill a large number of animals in a large vessel. It will 

 not do, however, to turn a saturated solution directly into sea water, 

 as precipitates would be copiously formed which would utterly ruin 

 the preparations. After the animals have sunk to the bottom of the 

 vessel, most of the water may be turned off, and 70 per cent, alcohol 

 added. In order to remove from the tissues the ferric salts adhering 

 to them, it is necessary to replace this alcohol with alcohol containing 

 a few drops of hydrochloric acid. 



The " fixation " of the animals in an expanded life-like form is 

 perfect, and the action of the dilute acid is of so short a duration that 

 it causes no injury to the tissues. Not only infusoria and Ehizopods, 

 but also large pelagic animals, such as Medusae, Ctenophora, Salpas, 

 Heteropods, Doliolum, &c., may be thus killed and transferred to 

 alcohol, with their form, histological structure, and cilia perfectly 

 preserved. After complete removal of the yellowish colour due to 

 the presence of ferric salts by washing in acidulated alcohol, the 

 tissues of transparent animals remain almost free from cloudiness. 



The best method of staining such objects is to add a few drops of 

 gallic acid (1 per cent, solution) to the alcohol. After twenty-four 

 hours the alcohol is turned off, and pure alcohol added. Thus treated, 

 the protoplasm will take a light-brown colour, the nuclei a much 

 deeper brown. Carmine stains too deeply and diffusely, and cannot 

 be successfully removed. 



Action of Tannin on Infusoria.! — H. Gilliatt, struck with the 

 remarkable appearance shown in Mr. Waddington's illustrations 

 (vol. iii. (1883) p. 185), made a number of experiments with glycerole 

 of tannin, as described by him. On exposing Paramecium aurelia to 

 the action of the tannin, he found the effect quite as startling as 

 described ; the animalcules, as the acid began to affect them, darted 



* Zeitschr. f. Wiss. Zool., xxxviii. (1883) pp. 491-2. See Amer. Natural., 

 xviii. (1884) pp. 218-9. 



t Proo. Liim. Soc. N. S. Wales, viii. (1883) pp. 383-6. 



