IN THE CHEILOSTOMATA. 



361 



the middle of the transverse bar forming the base of the mandible. 

 In one or two instances I have fancied that this little projection 

 was beset with short upright setce ; but I am by no means sure of 

 this observation, as I have almost universally failed to perceive any 

 thing of the kind. But should it be found in recent specimens, and 

 under very favourable circumstances, that this languette is so 

 furnished, one might suppose that it formed a sort of tactile 

 organ, the touching of which might induce the sudden closure of 

 the mandible. It might thus, though differently placed, be taken 

 to represent the apparently tactile organ long ago noticed in some 

 other avicularia (see woodcuts J & K). But a curious point 

 connected with this little appen- 

 dage is, that it is not found in any 

 of the " schizostomatous" Celle- 

 pores, so far as my observation 

 goes, but seems to be limited to 

 the holostomatous species belong- 

 ing to the southern hemisphere 

 alone. 



It remains to say a few words on the method I have found most 

 convenient for the procuring of the chitinous elements for the 

 purpose of examination. It is, however, extremely simple and 

 easy, consisting merely in the removal of the calcareous matter 

 from the fragment or specimen to be examined, by immersion for 

 a short time in dilute nitric acid, and, after it has been washed 

 with as little disturbance as possible, staining the flocculent residue 

 with picro-carmine. It should then be teased to pieces in a drop 

 of glycerine or gum and glycerine &c. and examined under a 

 covering-glass. All the chitinous parts will, in this way, be dis- 

 played of a bright yellow colour. 



This mode of preparation, moreover, has the advantage of dis- 

 playing in great perfection nearly all the soft animal tissues, if 

 any such exist in the specimen, however long it may have been 

 dried. The muscular tissue is especially well displayed in this 

 way, in specimens that have been dried for thirty or forty years, in 

 almost as great perfection as if the specimen had been living ; and 

 I have little doubt that any one versed in the modern methods of 

 histological research will be able to make out in specimens of 

 almost any age, if originally in proper condition, and especially 

 if they had been killed by immersion in spirit, almost as much as 

 could be found in a perfectly fresh subject. In one instance, in a 



