480 W. JR. Coe — Anatomy of Cerehratulus lacteus. 



ning water. If corrosive sublimate or water be employed the speci- 

 mens should remain but one or two minutes and then be transferred 

 to alcohol of TO per cent., which must be changed repeatedly. A 

 two per cent, solution of formalin in 50 per cent, alcohol also gives 

 good results. 



For killing the sjDecimens a solution of 0.5 to 1 per cent, formalin in 

 sea-water gives excellent results. In this fluid the worms die without 

 contraction, with their proboscides in place, and are nicely preserved 

 for histological study. After a few minutes the animals should be 

 transferred to weak alcohol, which should soon be changed to strong 

 alcohol. 



Good museum specimens, or material for class-room work, can be 

 preserved, perhaps permanently, in a three per cent, aqueous solution 

 of formalin. Specimens preserved in this way nearly a year ago are 

 as yet in an excellent state of preservation, even for histological 

 study. By making a few horizontal and transverse sections of such 

 specimens, the student can readily obtain a good idea of nemer- 

 tean anatomy ; or the brain and other organs may be easily dissected 

 out from a specimen which has been kept for several days in a one 

 per cent, solution of formalin. For sectioning in'parafiin the worms 

 may be stained in toto with borax-carmine, Mayer's hgemalum, or 

 carmalum. In using borax-carmine, a little picric acid may be 

 added to the benzole or xylol which is used for dissolving the par- 

 affin from the sections on the slide. The best results, however, 

 cannot be obtained by staining in toto. It is often convenient to 

 employ a preliminary stain in toto with borax-carmine, or perhaps 

 better with an analiu, in order that the paraffin blocks may be more 

 readily oriented than would be the case were the specimens unstained 

 and almost colorless. The sections, after having been cut, are fas- 

 tened to the slides with Mayer's albumen and restained with Dela- 

 field's hgematoxylin diluted with an equal quantity of water. After 

 washing off the superfluous stain with water, the sections are passed 

 through a solution of Griibler's orange, G, in 35 per cent, alcohol. 

 This method gives the tissues a beautiful purple nuclear stain with 

 an. orange plasma-stain. 



In studying the histology of the tissues it is necessary to isolate 

 the individual cells by means of maceration. For this purpose 

 nothing has given better results than an aqueous solution of less, 

 than one per cent, formalin. One-fifth of one per cent., or even less 

 is for some tissues strong enough. After a day or two the cells are 

 readily separated and their nuclei stain with great intensity with 

 Delafield's hsematoxvlin diluted with water. 



