DEVELOPMENT AND DURATION OF LIFE IN IN^i I- \~ 



from his experiments on the starvation of leeches as well as from 

 the papers by several authors on other animals the conclusion 

 supported by numerous grounds that fat has no great import. in. v 

 in the hunger nirt.iboli-m of cold-blooded animals, but that it 

 undergoes only small reduction. The farther investigations of 

 Hialas/ewi<-/ will undoubtedly show whether my supposition 

 based on histological research is right, or they may explain the 

 cause <>f this discrepancy which possibly consists in the physio- 

 logical capacity of caterpillars to digest their store of adipose 

 tisane during their frequent moults. 



In contemporary research the cause of natural death is regarded 

 ui>ed by the accumulation of detrimental products of normal 

 metabolism which cannot be removed from the mtilticellular 

 organism. This view is not at all proved; it is based first of all 

 on the known investigations of Woodruff on the infusoria whose 

 conclusions are in discrepancy with the results obtained by 

 Viewegerowa and \ ieweger ('22) who by methodically exact 

 research proved that the products of metabolism have no great 

 importance on the development of Colpidium and tli.it tin- di\i- 

 sions are hindered in unchanged surroundings first of all by inani- 

 tion. Ii nevertheless seems to me to be unquestionable th.it the 

 duration of life depends on the character of metabolism, in oilier 

 words, that natural death is a function of metabolism. The 

 experiments performed by Kellogg and Hell ('04 b), by 1'ietei 

 <>j) and by Northrop ('17) on larva? as well as those 1>\ I .oeb 

 .UK! Northrop ('17) on fully-developed insects of 1 )n.-o|)liila 

 simu th. LI by means of inadequate food we may elicit considerable 

 changes of the duration of development or of life of tin -< igan- 

 i-ms. As investigations on the hunger metaboli-m e\ idence 

 distinct differences of the digested substances, .md <>t tin- character 

 of their disintegration in comparison t" normal nu-tabolism, it 

 ought to be inferred that, if death i- a I'UIH lion oi iiH-tab.li-m. 

 insufficient feeding may also influence the in.mirnt of natural 

 death. Schultx ('05) emphasixes that certain animals under- 

 going periods of hibernal (or ,r-tival) sleep which is < . .ntu-i i-.-d 

 with \'er\' restricted metabolism live \ ery long in com]i.iri-on 

 with those having no such periods of rest. Stn must be laid 

 on the fact that in my experiments moths deriving from starved 

 caterpillars in which the development was much prolonged or 



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