680 THE POPULAR SCIENCE MONTHLY. 



Since the oldest times attempts have been made to find some feat- 

 ures characteristic respectively of animals and of plants. But all of 

 these criterions, one by one, have had to be abandoned. Finally, 

 Haeckel, of Jena, severed the Gordian knot. He created an inter- 

 mediate realm to which all is consigned that is not distinctively a 

 plant or an animal. Now, however, the difficulty is only greater than 

 it was before. Formerly the question was, Animal or vegetable king- 

 dom ? Now it has become, Animal, protista (for thus Haeckel named 

 this new division), or vegetable kingdom ? 



This system of classification at least affords us a general view over 

 those organisms which are, as it were, the connecting links between 

 the vegetable and the animal world, between which, at first sight, there 

 seems to be an impassable chasm. 



The slime-fungi have before been alluded to ; the class of fungi 

 embraces yet other groups that, as animal-plants, call for some notice 

 on our part. Above all must be named the bacteria ; in 1853 these 

 organisms were relegated to the vegetable kingdom. In the case of 

 many bacteria, motion can be observed ; some move quietly about, 

 others slide and glide to and fro like snakes or eels. A few species 

 are provided with special thread-like filaments for this purpose. Some 

 bacteria, as well as many other kinds of organisms, can withstand — 

 that is to say, survive — considerable heat. There are, for instance, the 

 algae in the waters of the Carlsbad Sprudel ; they attain luxuriant 

 growth at a temperature of 54° C. Other species of this kind live 

 though exposed to the hot vapors (about 65° C.) of Ischia and Liparia. 

 This is all the more remarkable as protoplasm, the albuminoid sub- 

 stance on which the phenomena of life depend, curdles at a much 

 lower temperature. 



A similar tenacity of life has been observed also in plants of a 

 higher order. Wheat-kernels, for instance, if they have been pre- 

 viously well dried, lose the property of germinating only at 72° C, 

 barley at G5° C. ; if moist, however, they die at a temperature of about 

 50° C. The seeds of many leguminous plants can not survive a tem- 

 perature of 35° C. Pouchet, however, has observed that seeds which 

 were found in the unwashed wool of Brazil sheep resisted for four 

 hours the action of boiling water. The hard seed-shells had prevented 

 the entering of the water. Haberlandt in 1863 made experiments with 

 the seeds of eighty-eight different kinds of cultivated plants, and 

 found that some of them could, when in a perfectly dry condition, 

 stand, for forty-eight hours, exposure to a temperature of 100° C. ; in 

 some instances, in fact, germination was hastened by the higher tem- 

 perature. Nor is the power of germination always destroyed by in- 

 tense cold. Tbis is demonstrated by the fact that, of three hundred 

 wheat-kernels which were left north by the Polaris in 1871, some sixty 

 germinated in 1877. 



Let us now turn our attention to a different group of organisms, 



