1909-1910-] Alg(E and their Study. 233 



chlorophyll, and therefore able to assimilate carbon from in- 

 organic matter. Previously a great number of exceedingly 

 small green objects, which, although containing chlorophyll, 

 led a roaming life, swimming freely in the surrounding water, 

 were identified with the so-called Infusoria of the naturalists 

 of the eighteenth century, and were therefore considered 

 animals. So long as the view prevailed that free movement 

 was a privilege confined to the animal world only, no objection 

 could be offered to this arrangement. When, however, the 

 zoospores of numerous filamentous Algae had been observed, 

 some naturalists asserted that the long-cherished dogma that 

 animals and plants were absolutely distinct had to be replaced 

 by more modern views. To use the words of a famous 

 scientist : " There is no difficulty in understanding that an 

 ox is an animal and an oak a plant, but if we go lower 

 down to the realm of the unicellular plants and animals, it 

 requires a bold man to assert that a certain unicell is un- 

 doubtedly an animal and another again undoubtedly a plant." 

 At present an agreement has been arrived at between botanists 

 and zoologists to a certain extent, and some important classes 

 of Unicells, or Protists as they are sometimes called, have been 

 definitely conceded to the botanists, such, for instance, as the 

 Diatoms. Other groups are indeterminate, especially the 

 enormous number of unicellular organisms called Flagellatse, 

 with or without chlorophyll, and which will be found in most 

 zoological text-books, and at the same time in all the botanical 

 works of the same class. 



I have dwelt on this subject of the unity of plant and 

 animal, the two kingdoms springing from a common root and 

 indistinguishable in their more primitive types, as I think that 

 one of the chief interests of this subject lies in the fact that 

 just among the Algae we meet with those organisms which 

 might be called plants as well as animals. There are a great 

 many amateur naturalists who are equally attracted by the 

 zoological and by the botanical side of Nature Study. If they 

 cannot come to a decision whether to study botany or zoology, 

 the Algae offer themselves to their special attention for the 

 very reasons mentioned already. It must be stated here, 

 however, that the greater part of the Algae are decidedly true 

 plants. 



That the study of Algae has not previously proved a favour- 



