The President's Address. By Dr. C. T. Hudson. Ill 



brackish waters of a tidal river. It was precisely in such a locality 

 that I first found Brachionus MiJlleri, in water only faintly salt, and 

 at a height of 30 feet above the Severn. Ditches of this kind are 

 to be found all down the Avon, from the highest point that the tide 

 reaches to its mouth. As they approach the Severn, their water 

 becomes more and more brackish, and the preponderance of marine 

 species in them more pronounced ; so that it is easy to see how the 

 descendants of a fresh-water Eotiferon, passing slowly down the 

 river-side from ditch to ditch, may, in course of many generations, 

 come to endure the sea itself. 



In other cases the air-borne eggs may have dropped into the 

 pools, of every degree of brackishness, which usually skirt the shores 

 of our river estuaries. It is in such places, on the Scottish shore, 

 that Mr. John Hood has found so many new marine species ; and 

 where no doubt so many more are yet to be found. 



But the most noteworthy point about the above list is that the 

 number of distinct genera is so great. One would rather have 

 expected to find but four or five genera hardy enough to endure salt 

 water ; and yet here are no fewer than nineteen genera for the thirty- 

 four known marine species ; and, of these latter, seventeen species are 

 yet in the transitional state, inhabiting alike salt waters and fresh. 

 Still more curious is it to find that all the four orders are represented 

 and that Bliizota, Bdelloida, and Seirtopoda have each furnished a 

 contingent to the marine forms, as well as the more frequent Plo'ima. 

 It is, of course, rather startling to hear that Melicerta and Floscu- 

 laria are to be found inhabiting sea water ; but I know of no reason 

 why any doubt should be thrown on Dr. Weisse's record of having so 

 found them on the sea-shore at Hapsal. 



The capacity of the Eotifera, for adapting themselves to new 

 surroundings, is shown by a mere enumeration of the strange places 

 in which they are found. For these fresh-water creatures, the 

 common inhabitants of lakes and ponds, are to be found in brackish 

 ditches, sea-pools, the mud of ponds, the dust of gutters, in tufts of 

 moss, on the blades of wet grass, in the rolled-up leaves and in the 

 cups of liverworts, in the cells of Volvox, the stems and sporangia 

 of VaucJieria ; in vegetable infusions ; on the backs of Eniomostraca, 

 on their abdominal plates, on their branchial feet ; on fresh-water 

 fleas, wood-lice, shrimps, and worms ; in the viscera of slugs, earth- 

 worms, and Naiades ; and in the body-cavities of 8ynaptse. 



But the great variability of every part of the external and internal 

 structure of the Eotifera, points to their fitness for playing the 

 parts of cosmopolites. See how, in Floscularia and Stephanoeeros, the 

 head and its appendages are so developed that they dwarf all the rest; 

 how in Apsilus the trunk predominates ; while in Actinurus both 

 head and trunk become appendages of a huge foot. The corona dimi- 

 nishes continually from the large complex organs of Melicerta, 

 Hydatina, and Brachionus, down to the furred face of Adineta and the 

 tuft of Seison ; and vanishes altogether in Acyclus. The antennae 

 can be traced from long infolding or telescopic tubes, furnished with 



