The President'' s Address. By Br. 0. T. Hudson. 175 



is curious that so delicate a thing should have borne the transport 

 safely. 



Dogs probably play only a humble part in the dispersion of the 

 Eotifera, but they cannot help taking some part in it ; by intercepting, 

 as they swim, eggs that are slowly sinking to the bottom ; or by 

 brushing off, on to their coats, eggs which have been already caught 

 by the weeds. For the ephippial eggs are frequently armed with 

 hooks or spines, which make them adhere easily to a pond-weed or to 

 a hairy coat, and yet would not prevent a dog's vigorous shake, after 

 his bathj from sending them flying into the air, or on to the dust, 

 where sun and wind would do the rest. 



Perhaps one of the most curious illustrations, of this aerial con- 

 veyance of Eotiferous eggs, is the account of Callidina symbiotica, 

 which we owe to Dr. Carl Zelinka. It was in the depth of last winter 

 that I read his interesting memoir concerning a new Callidina, that 

 he had discovered inhabiting the little green cups on the under 

 surfaces of the leaves of a scale-moss (FruUania dilatata). As 

 I knew that this plant grew on the elms of our Clifton promenade, I 

 started off at once on the rather forlorn hope of finding some living 

 specimens of the new Eotiferon. When I arrived at the promenade 

 I passed patch after patch of the scale-moss, hoping in vain to find 

 something more promising than the withered, liver-coloured stuff, which 

 alone was to be seen on the tree-trunks. At last I gave up further 

 search, and pulling off a scrap of what looked like old ragged carpet, 

 I carried it home. There I put a bit of it into a watch-glass, covered 

 it with water, and gently teased it out with needles, till I found an 

 under-frond that had some pretension to being green. This I trans- 

 ferred to a glass cell, and placed it under the Microscope with the 

 cups turned towards me ; and it was with no little pleasure that, in 

 about a quarter of an hour, I saw first one Callidina and then another 

 stretch its proboscis out of a cup, unfurl its wheels, and begin to feed. 



No wonder that these Philodinidm are to be found everywhere 

 when they can bear to be frozen alive in the cell of a plant, or roasted 

 by a midsummer sun in a leaden gutter. 



Some chance breeze must have first wafted a Callidina s egg on 

 to the scale-moss, just after a shower, when the whole plant was wet, 

 and the little green cups were filled with water. The young Calli- 

 dina, when hatched, could not have desired a better home. The 

 rainfall, on an elm, flows down its furrowed bark in tracks as constant 

 as those of a river and its tributaries ; and the growth of the Junger- 

 man follows these tracks. Every shower fills the spaces between its 

 flat layers of overlapping leaves with water ; and the lower layers, 

 sheltered by the upper, retain for a long time water enough for the 

 Callidina to creep about or swim in. And when at last the sun and 

 air have dried up the water, the creature retreats into its green cup, 

 which presents so small an aperture to the air, and is so fenced round 

 with thick juicy cells, that the contained water is almost certain to 

 hold out till the next shower. If it does not, the Callidina is still 



