76 THE SHORE 



looking mess, with much sediment, in which are the 

 animals ; it may be preserved by adding one-twentieth 

 of its volume of ordinary commercial formic aldehyde 

 (a 40 per cent, solution, see p. 347), leaving the sorting 

 out of the different animals to be done in the laboratory 

 of a colder climate. 



While individual genera of the last groups of animals 

 are adapted to almost every environment, most other 

 groups of free-living forms are adapted to some par- 

 ticular environment. Thus Amphioxus of different 

 genera all live in sand, though they pass their larval 

 existence as pelagic animals. Such sand must be clean 

 (sharp, as it is termed), and preferably in such a position 

 that it is slightly stirred by the rise and fall of every 

 tide. Even if present, Amphioxus is generally local, 

 but where it occurs it is enormously abundant ; large 

 numbers may be readily obtained by sifting the sand 

 through one or a series of sieves of different mesh 

 fitted into one another, which are held while being 

 shaken just submerged in the sea water. Equally 

 sand-loving are Balanoglossus and its allies, but the}' 

 prefer either rather dirty sand-flats, into which they 

 burrow (throwing up great mole-heap-like mounds of 

 the sand which has passed through their bodies for 

 food), or else the rather shallow accumulations of sand 

 under or in the crevices of stones, where they get out 

 of the reach of the other forms of life which might prey 

 on them. A slight smell like cyanide or " prussic 

 acid " in the sand is a sure sign of their presence, while 

 a smell of sulphuretted hydrogen (rotten eggs) may, 

 practically speaking, be taken to indicate the absence 

 of most forms of animal life. The author's receipt for 

 the sand-living forms is to rind a flat of sand overlying 

 a bed of rock a foot or two below. The collector will 

 see at once if there are any mounds, and, if so, he will 





