Infiiience of Environment upon the Organism. 457 



influenced directly. It would be idle to assert that flowers 

 had suffered no mechanical modifications from the visits of 

 insects, or that ants and other visitants have come and gone 

 for millennia without leaving traces of their direct work. 

 Especially where organisms have become constantly associated 

 does the influence make itself markedly felt. Thus Semper 

 (204) notes how the influence of sea-spiders {Pycnogonidm) 

 on Hydroids acquires the constancy of a specific character, 

 and refers to the mutually influential associations of a 

 Buccinum and a Gorgonia, of an Annelid and an Antipathes. 

 The characters of Tuhularia parasitica lately described by 

 Korottneft" (199a) cannot be understood apart from the 

 limitations of the Gorgonia which it inhabits; and F. E. 

 Schulze (203), in his recent Eeport on the " Challenger " 

 Hexactinellida, notes how commensal polypes {Stephoscyphus 

 mirabilis) have wholly altered the form of a sponge Myxilla. 

 Kossmann (204) explains the asymmetrical growth of a 

 parasitic Crustacean (Tachyhdella) as the direct result of 

 pressure, as at first abnormal, but now inherited. Giard 

 (198) has lately described how the parasitic Crustacean 

 Sacculina, infesting the sharp-beaked crab Stenorhynchus, has 

 affected copulatory appendages and other sexual characters 

 almost to the degree of castration. In a later paper (199) he 

 has given other instances. That parasites (200) may exert 

 distinct influence on their host, as well as mce versa, goes 

 without saying ; inflammation, rupture, choking, deterioration 

 of juices, and other effects less disadvantageous, may result ; 

 and Eoux (202) notes how even changes in the capillaries and 

 histology may be effected by a parasite. That true symbions 

 must have an important influence on function is also obvious. 

 A simple reference to the direct influence of man in domes- 

 tication may fitly close this catalogue of environmental 

 influences. 



6. Physiological ClassificcUion of Results. — The environ- 

 mental influences may also be classified according to the 

 various systems affected. Such a classification, from the 

 organism point of view, might follow the usual series of 

 systems, as indicated in the middle column of my table. 

 Certain conditions, especially of a mechanical and quantita- 



