70 PROCKEDIXGS OF THE 



Mr. S. L. Moore followed with a paper " A Contribution totlie 

 Flora of Australia." 



Dr. A. B. RencUe ])oinle(l out the iuterest of this paper, and 

 the curious fate which had befallen so many tine collections of 

 Australian plants, as those of JJanks and Colander, Eobert Brown, 

 and others. 



The reniaininji; papers, in the absence of their authors, were 

 read in title : — " Selenariada; and other Biwozoa," by Mr. A. W. 

 AVatkus, F.L.S. 



jVext followed " Studies on some Flagellata,'" by Dr. E, Penahd, 

 F.M.L.S. 



The last paper was by Dr. Walter M. Tattersall. and 

 communicated by Prof. W. A. Herdman, F.E.S., F.L..S., '• Eeport 

 on the Stomatopoda and Macrurous Decapoda collected by 

 Mr. Cyril Crossland in the Sudanese Ked Sea." 



Dr. J. R. Leesox, F.L.S., exhibited Lemna minor in flower, 

 under a simple magnification. 



ABSTRACTS. 



The 'Law of Loss' in Evolution. By Agnes Arber, D.Sc, 



F.L.S., Fellow of jS'ewnham College, Cambridge. 



[Kead 7th Noveiuber, 1918.1 



DuBiNtr the last eight years I have been making a special study of 

 aquatic Angiosperms. These plants are of particular interest from 

 the evolutionary stan(l|)oint, since there is a firmer basis for 

 speculations as to their ancestry than is generally available in the 

 case of groups concerning whose histoiw we have no fos>il evidence. 

 There is good reason to believe that the Flowering Plants were 

 originally a terrestrial stock, and we are thus juslitied in 

 concluding tliat the aquatic Angiosperms of the present day are 

 ultimately derivable from ancestors which were land plants. As 

 compared with their terrestrial relatives, the most obvious 

 changes which aquatics have suffered lie in the direction of 

 structural rwduction. This is fully recognized, and has indeed 

 become a text-book platitude. The consideration of this reduc- 

 tion, and of some phenomena which seem to be its sequels, has 

 led me to formuhite, under the name of the ' Law of Loss,' a 

 certain minor principle which appears to be operative in various 

 phases of plant evolution. The expression ' Law of Lots' is meant 



