XOTES. 449 



what, to my knowledge, other travellers had already described that 

 the Ampullarias breathe not merely with both gills and lungs, but that 

 they do so in regular alternation; for a certain time they inhale the air 

 at the surface of the water, forming a hollow elongated tube by incurv- 

 ing the margin of the mantle, so that the hollow surface is enclosed 

 against the water, and open only at the top. When they have thus 

 sacked in a sufficient quantity of air, they reverse the margin of the 

 mantle, opening the tube into which the water streams. The changes are 

 tolerably frequent, once or twice in a few minutes, depending, pro- 

 bably, on the temperature. No physiological explanation of the.se 

 rhythmic alternations can, however, be at present assigned. 



JTote 91, pa(,e 192. Fritz Miiller, the weil-known naturalist in 

 Brazil, in his admirable essay, Pacts and Arguments for Darrrin, has 

 given us a quantity of observations on the mode and way in which 

 crabs breathe air. The modes by which this is accomplished are very 

 various ; and even the structural relations implicated in the process, 

 which are sometimes extremely peculiar, irresistibly prove that the 

 different air-breathing Crustaceans no more constitute a natural family 

 than do the Labyrinthici among fishes. 



Xote 92, page 193. In a few works, distinguished for their dogmatic 

 sty'e, and intended for the use of students in medicine, it is stated that 

 these land-crabs, and above all Birgm latro, breathe no air, but only 

 water, and that the branchiae are exclusively the organs of respiration. 

 I cannot understand how so incorrect a statement can have become so 

 common, for the authors of these works cannot adduce a single experi- 

 ment which proves that in fact the introduction of oxygen into the 

 blood takes place exclusively by means of water, and through the 

 branchiae. Since absolutely no physiological experiments exist on this 

 subject, this erroneous view can only rest on an interpretation which 

 is acknowledged to be insufficient of the morphological features. So 

 far as here regards Birgus latro, I ha^e shown in the text, and in the 

 cut on page 5, that the views hitherto entertained as to the structure of 

 the branchial lungs of this animal are altogether false, and that every 

 morphological attribute is to be found in them which we should expect 

 to find in a true lung. 



JVi'fc 93, page 195. I have before alluded to the injury that may 

 sometimes result from a superabundance of air in water, by which so 

 large a supply may be taken in by a fish (a stickleback or an Axolotl) 

 that it may become lighter than the water and so unable to find its 

 food at the bottom. 



Xotc 94, page 198. Dr. August Panly. With regard to the last, 

 point alluded to in the text I must be allowed to make a few notes. 

 Pauly says that Lymnaaae, when they are kept under water and 

 have no opportunity of inhaling air-bubbles into their lungs, keep tte 

 lungs closed. A mollusc, having its lungs filled with air, will absorb 



