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In the Aphrodita aculeata, the organs of respiration differ so much 

 from other animals of that tribe, that the author enters more minutely 

 into the peculiarities of their structure. There are thirty-two open- 

 ings between its tufts of bristles on each side, which lead to one large 

 cavity on the back, into which project two rows of globular cells that 

 communicate with the viscera, the use of which may admit of some 

 doubt. 



In the Leech, there are sixteen external orifices on each side under 

 the surface of the belly, communicating with an equal number of di- 

 stinct globular cells. 



With respect to the respiration of the Lamprey, the author observes, 

 that it naturally differs from that of fishes in general ; for whilst they 

 are attached by means of their mouths, the respiration could not then 

 be carried on by means of that organ. A portion of the respired 

 water may, however, be occasionally received into the oesophagus by 

 a tube, with which all the bags communicate, and thence may pass 

 into the stomach. 



In the animal from the South Seas, which has no cartilaginous 

 thorax, the respiration must be performed by the elasticity of the 

 bags themselves. 



In the Myxine, the author conceives that the water received by 

 the two external openings is carried wholly into the oesophagus, and 

 is then thrown out by an orifice that opens externally below those 

 before described. 



In the Aphrodita and Leech, the same openings which receive, also 

 emit the respired water ; and since in the latter the pressure of the 

 bags is affected by the muscles of the body, their respiration must 

 vary according to the degree of bodily exertion. 



On the Mode of Generation of the Lamprey and Myxine. By Sir 

 Everard Home, Bart. V.P.R.S. Read June 15, 1815. [Phil. 

 Trans. 1815,^. 265.] 



The present may be regarded as an addition to those reasons which 

 the author lately gave for placing the Lamprey and Myxine in a rank 

 intermediate between fishes and vermes ; for instead of having di- 

 stinct sexes, as is the case in perfect fish, Sir Everard Home observes 

 that they are hermaphrodite. 



He finds that the organs, which have been hitherto taken for kid- 

 neys in supposed females, are in reality testicles, and that the sup- 

 posed males are really fish without spawn, in consequence of their 

 not breeding two seasons together. 





