rEBETJAKY 26, 1915] 



SCIENCE 



311 



tions and immunity factors of the animal, 

 because of the limitations in knowledge. Ig 

 it not fair to suppose, however, that this 

 required material may be just as definite, 

 and may occupy in many cases the same 

 relationship to the organism as in the ease 

 of fermentation? 



Going a little higher in the scale of life 

 for a single illustration, Keeble^* contrib- 

 utes an interesting study of association in 

 Convoluta roscofensis. 



In its earlier youth Convoluta roscoffensis feeds 

 after the manner of animals in general, on other 

 plants and animals. This is the first stage. In 

 the course thereof green cells appear in the body, 

 increase, multiply, photo-synthesize and distribute 

 food material to the animal tissues. For a while, 

 Convoluta roscoffensis receives food from two 

 sources — ^from ingested plants and animals and 

 from its green cells. This second phase is suc- 

 ceeded by a third in which Convoluta roscoffensis, 

 having ceased to ingest solid food, is nourished 

 in the same manner as the colorless non-ehloro- 

 phyllous tissues of a green plant are nourished, by 

 the products of the photosynthetic activity of its 

 green cells. The last stage of all which ends this 

 strange eventful history: The animal digests its 

 green cells, and having done so dies. In the first 

 phase the mode of nutrition is animal- wise; in the 

 second, part animal, part plant -wise; in the third, 

 altogether plant-wise or holophytic, and in the 

 fourth auto-trophie, that is by living on itself. 



Interesting cases of animals and plants 

 higher in the scale than microorganisms can 

 be easily multiplied. 



The strenuous efforts of the laboratory 

 worker to find a medium for pure culture 

 studies seem to be provided in nature for 

 many organisms. What appears laborious 

 and complex to us in our artificial attempts 

 is simple and direct as a natural process. 

 Oftentimes associated products suggest the 

 missing compound for pure culture opera- 

 tions, as has been experienced so often, but 

 this frequently fails quantitatively or 



i*Keeble, F., "Plant-Animals — ^A Study of 

 Symbiosis," Cambridge Press. 



qualitatively through some neglected or un- 

 discovered by-product. 



In Pfeffer's disjunctive symbiosis many 

 possibilities exist, but whether they may be 

 regarded as a true biological association, 

 or by analysis may be included in his con- 

 junctive symbiosis, remains an open ques- 

 tion. 



Keeble's plant animals can be regarded 

 as independent in a sense, but, on the other 

 hand, they are very dependent. So too, the 

 poled lima bean needs support which may 

 in no manner be considered a part of its 

 metabolism. For its best development the 

 ivy needs a tree or stone wall ; still, they are 

 not biologically related. Because a strepto- 

 coccus may accompany diphtheria infec- 

 tions and produce complications, or the 

 tetanus organism is found in pyogenic 

 processes, it does not follow that diphtheria 

 is dependent upon streptococci or that the 

 pyogenic organisms are dependent upon 

 tetanus organisms, to appear in the pure 

 individual life. That these processes may 

 be modified or that these organisms of 

 diphtheria and tetanus are perhaps fostered 

 by association, will not be contradicted; 

 yet they may live as independent forms. 

 The pertinency of this class, therefore, 

 must find its answer in physiological de- 

 pendency or social independence with 

 favoring or antagonistic elements. 



If associations of microorganisms de- 

 pendent or otherwise are subjected to anal- 

 ysis, there may be traced through them all 

 some functional factor or principle as tem- 

 perature, oxygen supply, food supply or 

 condition of food (whether acid or aUcaline, 

 whether dry or moist, whether composed of 

 one class of elements or another), or the 

 production of metabolic products. For in- 

 stance, the oxygen requirements may be 

 illustrated by the growth of Clostridium 

 iutyricum in the presence of aerobic organ- 

 isms ; moisture by the elimination of many 



