198 Aids to Microscopic Inquiry. 



be less puzzled in our endeavour, hitherto so fruitless, to make 

 up the palasontological and zoological record of life, extinct 

 and existant, upon the earth's surface ; and hemitypic birds, 

 reptilian fish, creatures retaining through life rudimentary 

 limbs or organs, or embryonal characters, may appear as 

 significant of orders of fife existant in other worlds, perhaps 

 in a more typical or perfected form. We shall not be the less 

 wise if we are thus compelled to study the fauna and flora of 

 the earth as a fragment of a scheme of life, in which, may-be, 

 much is but shadowed to us, and some elements concealed 

 altogether. If increase of such knowledge as the author of 

 the paper suggests will lessen our' dependence on schemes 

 drawn from objects ocularly or tangible before us, it will 

 surely aid our faith in the wisdom and beneficence of the 

 Creator. 



AIDS TO MICROSCOPIC INQUIRY.— No. V. 



Simple Forms of Life. 



We do not propose to publish this series of papers in the 

 order in which they would be most logically arranged, as a 

 less regular method will afford more variety, and enable us 

 more quickly to meet the wishes of subscribers requiring dif- 

 ferent kinds of information. We shall, therefore, postpone the 

 further consideration of certain points of physical science 

 essential to microscopists, and devote our present attention to 

 Simple Forms of Life. We will suppose a collection of ordi- 

 nary objects obtained from a pond or clean ditch, by bringing- 

 home weeds as well as water, and that the student has thus 

 before him specimens of animals and vegetables the characters 

 of which will be more or less definite and distinct. The first 

 question a young microscopist puts is, " How am I to know 

 animalcules from plants ? " and, although the query may appear 

 easy of solution, the establishment of fixed fines of demarca- 

 tion not only remains a permanent difficulty, but at last a mo- 

 dification of the old notion of zoophytes, or animal-plants, is 

 actually revived, although, by no means including the objects 

 for which the designation was originally employed, nor sug- 

 gesting the precise ideas which the older naturalists enter- 

 tained. If we were to say that the simplest form of life con- 

 sists of a single cell, we must so far modify that term as to 

 make it comprehend a globule or molecule, in which there is 

 no special distinction of cell wall and cell contents. Properly 



