Preparation of Chick Embryos 377 



Decalcification can be undertaken Avith 3-4% nitric acid. If the soft 

 parts are to be fixed, wedge the valves apart Avith a small length of glass 

 rod and place entire animal in fixative. Dissect out after it is fixed. 

 Gills can be removed and fixed flat in a mercuric chloride fixative. 



ECHINDODERMATA. 



Inject fixative into the tip of the rays of starfish. This will extend the 

 feet. Then drop the animal in fixative; mercuric chloride-acetic is good. 



Staining Invertebrates 



Sections can be stained in any manner, depending on the fixatives and 

 the desired restilts. 



For beautiful transparent whole moinits, the carmine stains (page 

 382) are the usual choice for most of the invertebrates: obelia, hydra 

 and hydroids, Daphnia, bryozoa, medusae, flukes, tapeworms, small 

 annelids, tunicate and ammocoetes larvae to name a few. Biu Korn- 

 hauser's hematein (page 384) is an excellent substitute, particularly for 

 flukes and tapcAvorms. 



If the cuticle and mtiscle layers of fltikes and tapeAvorms tend to 

 remain opaque and obscure the details of internal anatomy, either of 

 the tAvo methods can be tried to correct the condition. Dehydrate and 

 clear in an oil, such as cedar oil. Place in a flat dish under a dissecting 

 microscope and carefully scrape aAvay some of the tisstie from both 

 surfaces. With care, this can free the animal of some of the dense tissue 

 material and not harm the internal structures. An alternate method is 

 to finish staining and then Avash in Avater. Transfer to a potassiimi 

 permanganate sohition made from a feAv drops of 0.5% solution added 

 to Avater until only a pink color develops. When the Avorm begins to 

 shoAv a greenish-broAvn sheen, remove it immediately to distilled Avater: 

 5 minutes. Transfer to 2-3% aqueous oxalic acid until bleached and 

 the sheen is lost. Wash thoroughly in running Avater at least one hour. 

 Dehydrate, clear, and motuit. 



References: Becker and Roudabush (1935); Galigher (1934); Gatenby 

 (1950); Gray (1952); Guyer (1953); Hegner, Cort, and Root (1927), and 

 Pantin (1946). 



Preparation of Chick Embryos 



The following procedure is a standard and simple one for removing, 

 fixing, and staining chick embryos of any size, from primitive streak to 

 age 96 hotirs: 



