BRITISH MARINE TURBELLARIA. 183 



ever, was not new. It had been discovered and carefully described by 

 0. F. Midler, in his ' Vermium terrestrium et fluviatilium Historia,' 

 nearly forty years before. While, therefore, Dalyell made no new 

 discovery in Planaria flexilis, his study of its habits considerably 

 increased our existing knowledge. 



The merit of his work lies in the careful and patient observatious, 

 the accumulation of many years, which it records. The muddy 

 haunts of the Jiexilis, its active behaviour when in search of food, its 

 inordinate appetite after a period of starvation (illustrated by a case 

 in which the bodies of three individuals burst and subsequently 

 putrefied, owing to the quantity of absorbed food), the increase in 

 bulk and changes of colour due to the contained nutriment, the mode 

 of propagation by eggs laid in batches like those of molluscs, and the 

 power of repairing serious injury, — all these points are graphically 

 described and extended to seven fresh-water forms. In fact, this book 

 contains even at the present time the best account that we possess of 

 the bionomics of these animals, and well earned for Dalyell the 

 dedication by v. Graff of his ' Monographie der Turbellarien.' 



From 1814 to 1852 the work done on this group was confined, in 

 this country, to the description of single forms, or to the records of 

 their occurrence on our coasts. Montagu (7) in 1815 discovered 

 Planaria vittata (Prosthecerceus vittatus) on the south coast of Devon- 

 shire. In 1821 Fleming (8) found Planaria atomata, tremellaris, and 

 vittata during a voyage round Scotland. Our knowledge of this part 

 of the British fauna was further increased by a series of papers by Dr. 

 George Johnson, and Wm. Thompson, of Dublin. The former, under 

 the title 'Illustrations of British Zoology' (11 and 12), described 

 Planaria cornuta (Eurylepta cornuta) and Planaria subauriculata 

 (Stylochoplana subauriculata) from the shores of Berwick Bay. These 

 accounts suffice to enable us to identify the species referred to, but 

 give little idea of their internal anatomy. The relations of the known 

 forms to one another were as yet quite obscure. Thompson recorded 

 forms from various Irish localities. Forbes and Goodsir found 

 Polyclads in the Orkneys and Shetlands in 1839 (13), and in his 

 later dredging reports Forbes frequently enters "Planaria sp.V 

 accompanied by a lament that so little is yet known of these forms. 

 If w r e turn to work done on the Continent during this period 



