468 CHAPTER XXXVI. 



Holothui'ids, Dr. Webrr informs me, are admirably pre- 

 served in formaldehyde; a weak solution is sufficient. 



For the staining of muscles with methylen blue, see Iwanzoi'f, 

 Arch. mih. Anat., xlix, 1897, p. 103 ; and for the study of calcareous 

 plates, see Woodland, Quart. Journ. Micr.Sci., xlix, 1906, p. 534 (fixation 

 with osmic acid, staining with picro-carmine, followed by Lichtgriin). 



894. Echinoidea.— I advise that they be killed by injection 

 of some fixing liquid. For preservation, formaldehyde has 

 proved admirahle in all respects, and greatly superior to 

 alcohol (Weber). 



Lo Bianco kills by pouring over them (mouth upwards) a 

 mixture of ten parts acetic acid and one of 1 per cent, chromic 

 acid, and brings at once into weak alcohol. Or he makes two 

 holes in the shell, lets the water run out and alcohol run in. 



Sedioihi of spines may be made by grinding, see § 177. 



Spicula and the skeleton of pedicellarise may be cleaned 

 by eau de Javelle, see Dodeelein {Wiss. Ergeh. Tiefsee-Eicj)ed., 

 V, 1906, p. 67). 



895. Asteroidea. — Hamakn {Beitr. Hi.'<t. Echinodcrmen, ii, 

 1885, p. 2) injects the living animal with a fixing liquid 

 through the tip of a ray. The ambulacra! feet and the 

 branchiae are soon distended by the fluid, and the animal is 

 then thrown into a quantity of the same reagent. 



In order to study the eyes, with the pigment preserved 

 in situ, they should be removed by dissection, should be 

 hardened in a mixture of equal parts of 1 per cent, osmic 

 acid and 1 per cent, acetic acid, and sectioned in a glycerin 

 gum mass, or some other mass that does not necessitate treat- 

 ment with alcohol (which dissolves out the pigment, leaving 

 the pigmented cells perfectly hyaline). For maceration use 

 one-third alcohol, the aceto-osmic mixture failing to preserve 

 the rods of the pigmented cells. 



Formaldehyde is )iot to be recommended for the preservation 

 of Asteroidea (Webkr). 



See also Lo Biakco, (.f. cit. (he kills Brisinga with absolute 

 alcohol), also §§ 17, 20. 



896. Ophiuridea should in general be killed in fre.^h water 

 if it be desired to avoid rupture of the rays (De Castellaenatj, 

 La Est. Zool. dn Napoles, p. 135). 



