Ixxxiv GENERAL SUMMARY OF SCIENTIFIC AND 



quent observation, can scarcely be overestimated a history 

 of a monad multiplying by subdivision, reproducing by con- 

 jugation (a true sexual reproduction of au extremely simple 

 type), and actually seen to develop from sporules invisible 

 under the powers usually employed in such investigations, 

 and indestructible by heat which is fatal to the adult forms, 

 it seems almost a waste of time to read of experiments with 

 boiled infusions in sealed flasks, and we are rather inclined 

 to wait patiently until Powell and Lealand or Tolles, or some 

 one else, shall give us a lens capable of reading the life-his- 

 tory, whatever it may be, of Bacteria and Vitriones." 



An excellent paper has appeared in the Quarterly Journal 

 of Microscopical Science on that other much-agitated subject, 

 Protoplasm^ entitled " Cell Theories," by Dr. Cleland. It is 

 evident, from liis review of the works of Strieker, Beale, and 

 Bennett, that "the protoplasmic element has assumed an enor- 

 mous importance, casting the nucleus into the shade, while 

 the reign of cell-walls has come to an end altogether." In 

 other words, it is not the cell, but the "nitrogenous substance 

 of an albuminoid character" wliich is of importance. But 

 yet to speak of life as a property of protoplasm, as Huxley 

 does, is in his opinion untrue. This substance is variable in 

 appearance and behavior, as is well illustrated by Heiden- 

 hain's observations on the differences in both salivary and 

 jzastric secretinc: corpuscles in states of activity and rest. 

 "How, then," asks Dr. Cleland, "shall we say that in its dif- 

 ferent conditions tlie material which constitutes tlie mass of 

 such corpuscles is one and the same chemical substance ? "We 

 shall, indeed, take a very imperfect view of the living units 

 to which an unhappy chance has given the unfortunate name 

 of cells, if we say that because neither cell-wall nor nucleus 

 is an essential element, therefore life is a property of proto- 

 plasm." 



That it is impossible for naturalists to tell the difference 

 between the lowest animals and the lowest plants seems 

 agreed upon. Haeckel has even, as others before him had 

 done, referred such forms to a distinct kingdom in nature. The 

 last essential difference thou2:ht to exist between animals and 

 plants of the lowest order was, perhaps, removed by Profess- 

 or Draper, who shows that plants, as well as animals, exljale 

 CJirbonic acid. Ilis article was published in 1872. During 



