INTRODUCTION 



chlorophylligerous plants must be regarded as derived from chloro- 

 phyll-bearing ancestors by adaptation to a food already somewhat 

 raised by other organisms above the lowest stage of carbon- 

 combination. 



Again, there are amongst the most highly developed flowering 

 plants examples here and there of the exceptional and special 

 development of stomach-like organs with mouth-like openings into 

 which insects are attracted, and when once entrapped are held 

 either by the actual movement of a grasping organ or by other 

 mechanical apparatus, and are digested by chemical secretions 

 identical in character with those of the animal stomach, the digested 

 product being absorbed and serving to nourish the plant. Such 

 cases, whilst they demonstrate in a most striking way the essential 

 identity of the faculties of the living protoplasm of plant and 

 animal, do not invalidate the fundamental proposition, that plants 

 are a series, of organisms which have developed their distinctive 

 form and structure as feeders on the diffused carbonic acid, ammonia, 

 and nitrates of the circumambient medium ; whilst animals are a 

 series which have developed their distinctive form and structure 

 as feeders on scattered often elusive live or dead bodies or solid 

 particles of other animals or of plants, that form being essentially a 

 locomotive sac with a mouth. Amongst the larger animals, those 

 visible to the naked eye, there are few exceptions to this rule. 

 Such exceptions are found in the obviously exceptional and therefore 

 aberrant internal parasites which require no mouth nor digestive sac. 



But there are a few, very rare cases of small aquatic animals 

 which are provided with chlorophyll-corpuscles and obtain a part 

 (in one case, the worm Convoluta, the whole) of their nutriment 

 in the same way as does the green plant, namely, in virtue of the 

 assimilation of carbon from carbonic acid in the chlorophyll- 

 bearing tissue when under the influence of sunlight. The 

 chlorophyll-bearing cells of the worm Convoluta and of many 

 Anthozoa have been shown to be unicellular parasites which have 

 established the closest relationship to their hosts. But it is by no 

 means demonstrated that the chlorophyll-corpuscles of Spongilla and 

 of Hydra are parasitic in origin. 1 The fact that they are not 

 chlorophyll-bearing cells, but simple non-nucleated corpuscles with 

 a cortex impregnated with chlorophyll precisely comparable to the 

 chlorophyll corpuscles of green plants, does not permit us to 

 consider them as parasites which have effected a lodgment and 

 association with Spongilla and Hydra with any more reason than 

 we can adduce for so regarding the similar corpuscles in green 

 plants. The view has been seriously advanced that the latter are, 



1 See on this subject my memoir on "The Chlorophyll-corpuscles and Amyloid 

 Deposits of Spongilla and Hydra" in vol. xxii. (1882) of the Quart. Journal of 

 Microsc. Science. 



