Formalin fixation - stains go in v. well at cert. length of time after animal in formalin - perhaps 2 months :': have to check every 2 months or whatever interval. Neutralize Formalin w. CaCO3 not Na2CO3 because of equilibrium & pH + saturatn. :'. use saturated CaCO3. Na2CO3 results in continual alk. solut as material is fixed Picric acid in water is better than an alcohol base for byggoens. Acids fix cells - alkali breaks down cells as attacks proteins Membranes fix well in methanol because of composition but soft tissues do not - so depend what you are studying Ectoderm implies a whole series of cells whereas epethelium specifies only 1 layer of special kind of cell. epitheran cuticle Note: Hyman, Fig. 110 p. 303 used cuticle epidermis peritoneum Great-grandfather. Acc. to G. ectoderm is embryol. term implying embryol. relations.