3] ACCLIMATIZATION TO DESICCATION 65 



for resisting desiccation is seen in the gemmules of sponges, 

 and Bryozoa, the eggs of many animals, and the spores of many 

 plants. Thus some protoplasm normally responds to the 

 stimulus of drought by going into desiccation-rigor. 



While, as we have seen, some protoplasmic bodies may be 

 dried as far as possible by the ordinary methods used in chem- 

 istry without death ensuing, other bodies, especially the adult 

 forms of higher organisms, whose cellular respiration is de- 

 pendent upon a circulating fluid, are killed by desiccation. 

 For loss of this fluid or desiccation-rigor in the pumping 

 muscles will produce asphyxia. But these conditions do not 

 militate against the belief that there is no necessary lower 

 limit to the amount of water which must occur in quiescent 

 protoplasm in order that it may retain vitality during a lim- 

 ited period. 



3. ON THE ACCLIMATIZATION OF ORGANISMS TO 



DESICCATION 



We have seen in the last section that certain organisms are 

 more capable of resisting desiccation without fatal effect than 

 others ; e.g. rotifers, tardigrades, and Tylenchus. Now it is 

 clear that these organisms are especially apt to become dried, 

 so that it is possible that their high capacity for resistance has 

 been produced by acclimatization without selection. I shall 

 here add certain other cases of resistance to dryness which I 

 believe, but cannot prove, to have been thus produced. LANCE 

 ('94) has mentioned, as already stated, that only those tardi- 

 grades which live in the moss of gutters (where they are 

 alternately wet and dried), and not those living in water, show 

 the phenomenon of revivification. CERTES ('92) has found 

 that, although marine Ciliata cannot, in general, withstand 

 desiccation, those from the chotts and saline lakes of Algeria 

 may be dried like those from fresh-water ponds and swamps. 

 The difference in resistance between the forms dwelling in 

 the sea and in inland salt-water ponds is doubtless due to the 

 fact that the former are not regularly desiccated, while the 

 latter are ; consequently the latter alone have had a chance to 

 become acclimated to desiccation. 



