The evolution theory . dthus a higher specific gravity, there isa predominance of species of Peridineaswith very short processes and relativelyundeveloped float-apparatus (Fig. 131,B). It could be seen clearly in thecourse of the voyage that the long-armed Peridinese became more abundantas the ship passed from the NorthEquatorial current into the Gulf ofGuinea, and that by and by they heldthe field altogether, but later, w^hen the Valdivia entered into the South Equa-torial current, they disappeared all atonce. Thus in this case, in which theveil over the relations between formand function in
The evolution theory . dthus a higher specific gravity, there isa predominance of species of Peridineaswith very short processes and relativelyundeveloped float-apparatus (Fig. 131,B). It could be seen clearly in thecourse of the voyage that the long-armed Peridinese became more abundantas the ship passed from the NorthEquatorial current into the Gulf ofGuinea, and that by and by they heldthe field altogether, but later, w^hen the Valdivia entered into the South Equa-torial current, they disappeared all atonce. Thus in this case, in which theveil over the relations between formand function in unicellular orsranisms ^ ^^^- ^3i- Peridmeae: species ot ^ . Ceratium. A, irom the Gulf of has been lifted a little, we recognize Guinea. B, from the South Equa- that the smallest parts of the cell-body ^^ currents. After Chun. obey the laws of adaptation, and consistent thinking must lead usto the conviction that even in the most lowly organisms the wholestructure in all its essential features depends upon 326 THE EVOLUTION THEOKY If the horns of the Peridinese grow to twelve times the usuallength in adaptation to life in sea-water with a salinity increased tothe extent of -002 per cent., then undoubtedly not only the proto-plasmic particles of the body which form the horns, but all the restas well, may be capable of adaptation: and if the Peridiniuon proto-plasm has this power of adapting itself to the external conditions,then the capacity for adaptation must be a general character ofall unicellular organisms, or rather of all living substance. As willbe seen later on, we shall be brought to the same conclusion bydifferent lines of evidence. But a recognition of this must greatlyrestrict the sphere of operation which we can attribute to saltatorymutations in the sense in which the term is used by De Vries, foradaptations from their very nature cannot arise suddenly, but mustoriginate gradually and step by step, from variations which com-bine with one another in a
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
