G. GENERAL NATURAL HISTORY AND ZOOLOGY. 261 



islands for the purpose of continuing his labors, informs the 

 editor of Nature that he also has obtained a pelagic fish-nest 

 similar to that described by Professor Agassiz, and possibly 

 of the same species. This was taken from some floating Gulf- 

 weed, and forms a mass about eight inches in depth by five 

 in breadth. The whole is thicker at the top, and woven to- 

 gether by fine elastic threads, forming a raft, from which 

 hanaj the clustering: masses of eecsrs, about the size of No. 7 

 shot. These threads are very strong, especially at their ter- 

 minal bases on the fucus sprays, where several are apparently 

 twisted together like the fibres of a rope. The sea-weed is 

 not only on the summit, but sundry sprays are interwoven 

 with the mass of eggs, thus rendering the fabric solid and 

 secure. 12.4, April 11,1872,462. 



RESPIRATION IX FISH. 



M. Grehaut, in the course of a lecture on respiration in 

 fishes, states that, as shown by previous writers, fish are able 

 to live in water until almost the whole of the oxygen it con- 

 tains in a state of solution has been exhausted. This was 

 shown by a chemical examination of some water in which 

 live fish were preserved, and which, after the expiration of a 

 certain time, showed an entire absence of oxygen, no change 

 in the amount of nitrogen, and double the amount of carbonic 

 acid. 



Another curious fact noted by the lecturer was that fish 

 breathe by their skin as well as by their gills, nearly as great 

 a change in the composition of the gases contained in the 

 water being observed when the animals were suspended up 

 to their branchia3 as when the whole body was immersed. 

 He also stated that the presence or absence of the swimming 

 bladder had little effect on the product of respiration. 13.4, 

 December 1,1871,538. 



GENESIS OF HIPPOCAMPUS. 



Canestrini, of the University of Padua, has lately discover- 

 ed that the young hippocampus, or sea-horse, a small fish 

 well known on our coast, is provided with a rudimentary 

 caudal fin, the adult lacking this appendage, the tail being 

 converted into a prehensile organ. A fossil fish ((^alamos- 

 tomus), however, from Monte IJolca, agrees with the young 



