438 Mr Eattray on the Distribution of 



part in the process of cross-fertilisation by influencing the 

 movements of the sometimes passively motile antherozoids, 

 and by affording shelter for small Amjjhipoda or other 

 creatures that by their movements aid in the dissemina- 

 tion both of antherozoids and of swarmspores. 



4. From the physiological standpoint, the more rapid 

 the growth of species on any given spot, tlie greater their 

 influence in oxidising the water, and consequently the 

 more active the movements of swarmspores emitted, and 

 the greater their chances of extending distribution, ciliary 

 action becoming less and less pronounced as the amount of 

 oxygen decreases, and increasing in activity with its increase 

 in volume within determinable limits. 



5. In cases where, artificially or otherwise, the change 

 of level of the water in inclosed basins becomes altered 

 (e.g., elevated), the change in the algoid facies is the more 

 sudden in proportion as the species are more rapidly 

 evolved. The great readiness with which specimens of 

 Laminaria saccharina appear in such circumstances is 

 especially noteworthy, 



The general data of distribution may be ranged in a 

 twofold manner, viz. (1) from a superficial or horizontal, 

 and (2) from a bathymetrical or vertical point of view. 



AYith respect to the bathymetrical range, J. G. Agardh,* 

 in 1836, pointed out that on the Scandinavian coastf three 

 algoid kingdoms could be distinguished from one another — 

 (1) Regnum Algariim Zoospermarum, (2) Regnum Algarum 

 OUvaceao'tcm, and (3) Regnum Algarum Floridearum. 



Up to a depth of 20 fathoms on this coast there is a 

 rich algoid growth, but beneath this it becomes more limited 

 and more uniform. Indeed, at greater depths than 25 

 fathoms, J. E. AreschougJ scarcely finds anything but 

 greatly reduced forms of Floridcce, especially Delesscria 

 sanguinea. Moreover, Kjellman § has recently (1878) 

 pointed out that the earlier kingdoms established by 

 Agardh are untenable, inasmuch as each " ist eine Zusam- 



* J. G. Agardh, "Novitice FloiEe Suecise ex Algainim familia," AJcad. Dis- 

 sert., Lundse, 1836. 



t In all the localities here quoted the species recorded agree in a very 

 marked manner with those found in the estuary of the Firth of Forth. 



t J. E. Areschoug, Phyc. Scaiul., p. 231. 



§ Bihang k. Sv. Vet, Akad. Haiidl., Bd. 5, Ko. 6, pp. 7, 8. 



