438 SOME ZOOLOGICAL METHODS. 



Similar methods are recommended by the same author for 

 the eyes of Heteropoda (see Abh. naturf. Ges. Halle-a.-S., 1886 ; 

 Zeit.f. wiss. Mik., 1886, p. 243). 



817. Eyes of Chitonidae (MOSELEY, Quart. Journ. Mic. Sci., 

 1885, p. 40). Moseley worked by decalcifying the shell and 

 making sections. He places fragments of shell (of which the 

 tissues have previously been hardened in strong alcohol) in 

 100 to 200 c.c. of distilled water, and adds drop by drop con- 

 centrated nitric acid until gas is freely given off, which gene- 

 rally happens when from 3 to 4 per cent, of acid have been 

 added. If the decalcification is not complete at the end of 

 twelve hours the objects should be removed to fresh distilled 

 water, and the operation repeated. This process is said to 

 give better results than the various processes of slow decalci- 

 fication. 



818. Eyes of Pecten and other Forms, see PATTEN, in Mitth. 

 tool. Stat. Neapel, vi, 4, 1886, p. 733. 



819. Shell. Sections of non-decalcified shell are easily 

 obtained by the usual methods of grinding, or, which is often 

 a better plan, by the methods of v. Koch or Ehrenbaum, 

 311,312. For sections of decalcified shell, MOSELEY, who 

 has had great experience of this kind of work, particularly 

 recommends the method of decalcification given above, 817. 



820. Injection of Acephala (FLEMMING, Arch. f. mik. Anat., 

 1878, p. 252). To kill the animals freeze them in a salt-and- 

 ice mixture, and throw them for half an hour into lukewarm 

 water. They will be found dead, and in a fit state for in- 

 jection. Chloroform and ether are useless (but see 16). 

 The injection-pipe may be tied in the heart ; but when this 

 has been accomplished there remains the problem of occlud- 

 ing cut vessels that it is impossible to tie. To this end, after 

 the pipe has been tied, the entire animal is filled and covered 

 up with plaster of Paris. As soon as the plaster has hardened 

 the injection may be proceeded with. 



821. Maceration Methods for Mollusca. For the study of 

 ciliated epithelium the following methods are recommended 

 by ENGELMANN (Pfliiger's Arch., xxiii, 1880, p. 505) : 



Cyclas cornea (intestine), maceration in osmic acid of 0'2 



