Observations on the Oribaiidpe. By A. D. Michael. 3 



suggested to me that the results may be of interest to one of the 

 biological societies, I have therefore described some of them in the 

 present paper, instead of waiting to include them for the first time 

 in the future treatise. I do not propose, in these pages, to give 

 any exhaustive account even of such portions of the anatomy as I 

 am acquainted with, that would be hardly fitted for this Journal, 

 and would certainly be too lengthy, but I shall confine myself to 

 such portions as seem to me to be undescribed, or to vary sub- 

 stantially from Nicolet's account, and to such other parts as are 

 necessary to the comprehension of the novelties. It is only fair to 

 Nicolet to point out, that, in his beautiful work above quoted, he 

 states, that, in consequence of the minute size, and the hard, 

 opaque, chitinous, exo-skeleton of these creatures, he found the 

 internal anatomy extremely difficult. Claparede gives a similar 

 reason for scarcely touching upon the internal anatomy. 



There cannot be any doubt that Nicolet and Claparede were 

 right as to the difficulty. The largest specimens are under a 

 millimetre in extreme length, and many of the species which I 

 have dissected are not above half that size ; they are possessed of a 

 chitinized cuticle which is nearly as hard and as brittle as glass, and 

 which is usually quite opaque at all times except immediately after 

 the ecdysis. I first tried observations at that period, but I soon 

 found that 1 could not obtain much information this way, for, 

 although, now that I am acquainted with the organs, I can 

 frequently recognize many of them through the dorsal plate during 

 its short period of transparency, yet the view is too imperfect, and 

 the organs too much hidden by one another, for original inquiry. 

 I endeavoured to stain them whole, but entirely failed in getting 

 any stain to penetrate the chitin of the exo-skeleton, or even to run 

 in at joints, stigmata, &c., although I tried the air-pump, hoping 

 it might assist. Finally, after a not very satisfactory attempt at 

 section cutting, I determined to face the difficulty of the small size, 

 and to rely entirely upon actual dissection — these notes are the 

 result. 



I soon found, that, in order to produce a successful dissection, 

 the creature must be in good, healthy, condition ; it must not have 

 been kept long in confinement, and it must be dissected immediately 

 after death. 



The dissections have, in each instance, been frequently repeated, 

 i. e. upon a considerable number of specimens of each species, as, in 

 consequence of the difficulties, the naturalist would be too liable to 

 error in judging from one or two instances. 



All the figures are made from actual dissections, they are not 

 calculated, or put together, from the result of consecutive sections. 

 The preparations from which the drawings are made, are, in almost 

 all instances, now in my possession, stained with logwood, and 



B 2 



