GAS GLA^^DS OF SOME TBLEOSTEAN' FISHES. 227 



which decomposition oxygen is to be produced (!), but oxygen 

 cannot be used up in decomposing tlie gland cells and yet be 

 available to fill the bladder space. And as regards the supposed 

 production of free nitrogen b}'^ the decomposition of the gas gland 

 cells, Jaeger might have pointed out that such a fact would be 

 unique in animal metabolism. Free nitrogen is not known to be 

 liberated by aiiy katabolic process. The only source of the free 

 nitrogen found in the bladder must be the small amount of that 

 gas dissolved in the blood plasma. But Jaeger's chief objection 

 to the theory of Nusbaum & lleis is the impossibility of accounting 

 for the high pressure of the gas contained in the bladder, if this 

 gas be simply produced by the decomposition of the cell-substance. 

 The generation of carbon dioxide from chalk at once ceases, he 

 points out, despite a high temperature, if the gas be allowed to 

 accumulate in the calcination chamber, and in the same way the 

 decomposition of cytoplasm would cease long before the liberated 

 gas could exert a fraction of the jDressure usually found in the 

 bladder *. Oppel (57), in a summary of papers by Reis & Nusbaum, 

 also objects that whilst these authors strongly insist ujjon cell- 

 degeneration yet they have not stated in what way the epithelium 

 is regenerated after periods of activity, and I also have been 

 unable to come to a conclusion as to the opinion held by Reis & 

 Nusbaum on this subject. In one paper (62) these authors state 

 in the last two sentences that they have observed mitotic figures 

 in the gland cells, and conclude that regeneration of the gland is 

 effected by ordinary cell-division ; in a subsequent paper (63), 

 however, they appear to embrace the curious view that the 

 amitosis first described by Deineka in Perca is a result of the 

 violent cell-decomposition associated, in their opinion, with the 

 activity of the gas gland, i. e. the nuclei, as well as the cytoplasm, 

 undergo disruptive changes, and that this amitosis (55) leads to 

 the production of new cells which take the place of those broken 

 up! Needless to say, I fail to see any justification for this 

 phcenix-like theory. My own researches have proved that the 

 cells of the gas gland, when worn out like other cells of the body 

 by a long period of activity, are replaced by ordinary mitotic 

 divisions of the small cells at the base of the gland and that 

 amitosis is only found in the later cell-generations. I may also 

 mention in connection with this necrobiotic or decomiDosition 

 theory of Nusbaum & Reis that, apart from other objections, it 

 has always seemed to me to expect too much from the individual 

 cell of the gas gland. The cell is not only requii^ed to commit 

 suicide by undergoing decomposition but whilst undergoing 

 decomjDosition it is to work energetically f in pumping the results 

 of its own decay into the bladder cavity. Even the cell of the 



* This particular objection of Jaeger is invalid since the decomposition of cyto- 

 plasm, being irreversible, would not be inhibited by pressure. 



t "The torniation of the gas bubbles in the cells is accompanied by fragmentation 



of the nucleus and simultaneous granular disintegration of the cell-plasma 



Condensation of the gas [in the cellj must accompany its formation since the lumen 

 of the bladder is filled with gas at a considerable pressure." Translation of Reis (64). 



