4 Transactions of the Society. 



If I had confined myself to these genera, the explanation of the 

 effects of glycerin would have been comparatively simple. I should 

 have concluded that it acted as a weak steriliser, or, more correctly, 

 retarder of decomposition, so as to make it possible to dry the 

 specimens before serious decomposition had taken place. To some 

 extent this explanation appears correct ; but the question, as a whole, 

 is far more complex ; and it seems to me that the successful prepara- 

 tion of specimens is almost entirely a question of the adequate 

 knowledge of a Somewhat peculiar branch of chemistry. I hope, 

 therefore, that the Society will not think the following remarks of too 

 chemical a character. 



The blood of the living animals is a fairly strong solution of 

 haemoglobin ; but in the final preparations the beautiful red substance 

 in the vessels does not give the well-marked absorption bands of 

 haemoglobin, but a spectrum like that given by blood dried on glass 

 and mounted in Canada balsam, from which the absorption bands 

 gradually fade, without any material change in the colour. It seems 

 to be a fairly stable product of a change occurring under such con- 

 ditions. It is, of course, important that the blood should not be lost 

 or altered in colour. It is also very necessary to more or less 

 completely remove the salt contained in the living animals ; since, 

 unless this is done, the mounted objects may be completely spoiled 

 by being filled to a surprising extent with crystals. What is wanted 

 is to let the animals remain just sufficiently long in glycerin and 

 afterwards in water, to remove the salt, but not so long as to lose 

 any material amount of blood. I am sorry that I am unable to say 

 whether or no ten minutes is the best length of time for each process, 

 and am inclined to think it ought to vary according to the species of 

 worm and its size ; and it might be better to use a stronger solution 

 of glycerin than that with an equal volume of water. It also appears 

 to me that there are individual differences in the same species, which 

 cannot be foreseen ; and, in the present state of the question, the 

 best plan is to prepare a number of specimens, and finally select 

 the best. 



Independently of its partially retarding decomposition, glycerin 

 and water seem to give better results than anything I have tried. 

 Diluted formalin rapidly changes the red colour of blood to a dull 

 brown. Though diluted alcohol is free from this objection, yet both 

 it and formalin are apt to make the specimens hard and not easy to 

 arrange on the glass, and the minute blood-vessels are lost, except in 

 such parts as dry very quickly. 



The decomposition of the body of the worms which obliterates 

 the blood-vessels, and in some species can be overcome by the use of 

 glycerin, seems to depend on some other substance in other species. 

 Thus, for example, though the blood-vessels of Arenicola are remark- 

 ably well developed, the employment of glycerin not only is useless 

 but seems to make the results worse than if not used. I have tried 

 over and over again, and could scarcely believe it possible to get such 



