106 Trniisacfidiif). 



iSphaeria are curiously gliding, and Uoating shell downwards ; 

 while further up, where peaty linns look bottomless, and the pike 

 gourmandises on everything he can get a hold of, with what a 

 sense of victory you haul in your bag net and, letting the muddy 

 water drip out of it, behold some new or rarely caught mollusk 

 in the hey-day of his spirits, wondering with his blind but 

 sensitive tentacles what in the world has come over the " spirit of 

 his dream " in the sunless depths where long-rooted pond-weeds 

 spread their canopy of dusky green. 



There are several points with respect to the life-iiistory of our 

 mollusks worthy of careful and patient observation and record. 

 For example, there is the controversy over Helix nevioralis and 

 H. hortensis to settle. We could each add our quota to the eluci- 

 dation of this vexed question were we to note whether these 

 reputed species breed together, whether they at all seasons are 

 found in one and the same locality, what their food is, what, in 

 short, are their points of resemblance and of distinction. In 

 carrying out the practical study of our L. and F. W. mollusks, 

 it is always well to note down, at the time of capture, what is 

 the plant they appear attached to, and, when coming indoors, 

 preparatory to killing your specimens in boiling, literally boiling, 

 water — the only merciful and instantaneous method of disposing 

 of them — to note particularly the general colour of the body, the 

 surface-texture of the back, and the shape of tentacles and "foot," 

 with an approximate indication of their length as compared with 

 the length or diameter of their shells. After leaving your 

 mollusks for a few hours in the water, a little neat and skilful 

 manipulation with a bent pin will, in nearly all cases, fetch out 

 the soft parts, leaving you with a shell more or less clear, but 

 always worth reverent examination, and revealing, under the 

 lens, curves of sculptured traceries and hues prismatic to an 

 amazing degree. Think for a moment of what has yet to be done 

 in ascertaining the causes of variation in species, sub-species, and 

 variety. There are certain species like Limnaea pereyra, whose 

 capacity for variation in shell form is something astonishing. 

 We could — or we may some day at any rate — arrive at a clue 

 which will help us in threading out towards the truth a path 

 through the labyrinths of these seemingly lawless creatures — 

 absolute Robin Hoods of the submerged forests of our tarns and 

 streams — if the facts of their lives and their general surroundings 

 were only narrowly and well watched. 



