SOME METHODS OP PREPARING MARINE SPECIMENS. 219 



the manufacturer's label either as formaldehyde 40 per cent, 

 or 30 per cent. The percentage should always be ascertained 

 at the time of purchase, and then it is a simple matter to make 

 up the solutions. Thus a 10 per cent, solution of formaldehyde 

 is made by adding 300 c.c. of water to 100 c.c. of the stock formal- 

 dehyde 40 per cent., and this will be found a very useful standard 

 solution for general purposes. I always keep on my work-table 

 two standard solutions, namely, the 10 per cent, and a 4 per cent, 

 solution made by adding one part of formaldehyde 40 per cent, 

 to nine parts of water. The 4 per cent, solution will be found 

 most useful for preserving many delicate organisms ; while fish-eggs 

 and embryos are best mounted in deep cells filled with this solution. 



Amphipods, copepods, and the larval stages of the Stalk- 

 eyed Crustacea may be kiUed with 4 per cent, formaldehyde in 

 sea-water, and then transferred to 70 per cent, alcohol. All 

 the Crustacea require careful handling in staining, as they easily 

 over-stain. It is preferable to use either a weak alcoholic picro- 

 carmine, or Mayer's alcoholic cochineal stain, the latter often giving 

 very beautiful results. After staining and dehydrating, clear 

 the Crustacea in Turpineol, which does not render the specimens 

 too transparent, but beautifully translucent. From the Turpineol 

 the specimens may, with advantage, be washed in xylol before 

 mounting in xylol-balsam. 



Sponges brought home from the rocks in a jar of sea- water are 

 taken out and plunged into a 1 per cent, solution of osmic acid, 

 and left for five minutes or longer according to size, and are then 

 placed in strong alcohol, which should be changed two or three times. 



Sections stain nicely with Mayer's alcoholic cochineal. 



The larvae of Spongilla are allowed to settle down on a large 

 cover-glassj and then fixed for three minutes in absolute alcohol. 

 They are then stained in alcoholic carmine, passed through graded 

 alcohols, cleared in oil of bergamot, and mounted in balsam. 

 This is the original method employed by Delage. 



The following is a method used for many years in cases 

 where time has been limited, for the wholesale preserving of the 

 tow-net catch : 



The receptacle to contain the catch consists of a glass pickle- 

 jar of some half-gallon capacity, with a good, deep, tight-fitting 

 cork. Through the cork two cleanly cut holes, about three- 

 quarters of an inch in diameter, are bored, and into one of these 



