SEA-FISHERIES LABORATORY. '293 



Preserved specimens were generally used and the dissec- 

 tion was performed under 70 per cent, spirit.* The 

 specimen was opened in the usual way and pinned out on 

 a piece of weighted cork in a small glass dish, and the 

 alimentary canal carefully removed. The specimen and 

 the cork were then put into stain, either carmine or 

 Mayer's acid hsemaluni, for 12 to 24 hours. After the 

 excess of stain had been removed the worm and the cork 

 were jDassed into 90 per cent., and then into absolute 

 alcohol. The body wall, which by this time was 

 moderately certain to retain its shape, was unpinned, and 

 after another change of absolute alcohol was placed in oil 

 of cloves and afterwards mounted in balsam. Fig. 25 was 

 drawn from such a preparation, in which the blood-vessels, 

 &c, are very clear. Useful preparations may also be 

 made by splitting the anterior portion of preserved 

 specimens into two by a median sagittal cut. Such 

 sections give a good idea of the position and relations of 

 the nuchal organ, diaphragms, proboscis, &c. 



Preparations of the Coelomic fluid may be made thus. 

 Immediately after the fluid is removed from the animal 

 spread a small drop evenly over the middle of a glass 

 slide so that it forms a very thin film. This may be 

 treated in either of the two following methods : — 



(1) Invert the slide so as to bring the film over the 

 mouth of a bottle containing glacial acetic acid and hold 

 it there for several seconds. The vapour of the acid will 

 kill and " fix " the cells, i.e., Avill coagulate their proto- 



*If a fresh worm be used, after the dissection under sea water has 

 been completed, the specimen should be "fixed" in a saturated 

 solution of corrosive sublimate. In this case, however, the dissection 

 should be pinned out with cactus needles, and not with ordinary pins, 

 as the latter would produce a deposit of mercury in the neighbouring 

 tissues. After fixation wash in water and in 50 per cent, and 70 per 

 cent, spirit, until all traces of sublimate are removed. Then stain as 

 directed. 



