president’s address. 
123 
The liftii memoir (1830) is another classical work, which 
contained the first proof that certain Zoophytes which had till 
then been associated with the Hydroids have a structure which is 
essentially different from that of Coelenterates. Thompson here 
introduced for these Zoophytes the term Polyzoa, which is used, 
alternatively with Ehrenberg’s name Bryozoa, as the class-name of 
this group of animals. 
These results, which are by no means the only ones with which 
Thompson’s name is connected, are a sufficient illustration of the 
advantage of a close observation of living animals. 
Another writer, whose studies of the habits and life-histories 
of marine Invertebrate animals were attended with conspicuous 
success, was Sir John Graham Dalyell. An account of the life and 
work of this remarkable man, who died in 1851, is contained in 
the third volume of his work, ‘The Powers of the Creator,’ 
which appeared, after Ins death, in 1858. This work, and his 
earlier treatise, ‘Rare and Remarkable Animals of Scotland’ 
(1847, 1848), abound in accurate and well directed observations, 
accompanied by excellent figures, on the habits and structure of 
many marine Invertebrates. The discovery of the life-history 
of the common Jelly-fishes of our seas, described in the first 
volume of the * Rare and Remarkable Animals of Scotland,’ may 
well serve as a model of the way in which such investigations 
should be carried on. 
It is true that the elder Sars had in 1835 given an admirable 
account* of the formation of Ephyrae by the transverse division of 
the so-called Strobila, and of the development of this stage from 
the Scyphistoma ; although he had not ascertained that the Ephyra 
was a young form of the well known Aurelia aurita. But 
Dalyell’s work was entirely independent of that of Sars, and his 
demonstration of the life-history was more complete. The Hydra 
tuba , or Scyphistoma , was found by Dalyell on the inner side, of 
empty bivalve shells, its body measuring five lines in length. The 
specimens at first observed were kept for two years and a half, 
* “ Beskrivelser og Iagttagelser over nogle maerkelige eller nye i Havet 
ved den Bergenske Kyst levende Dyr,” p. 16. 
