riBKOUS TISSUE PKODUCED AS A REACTION To JXJIT1{A\ 597 



per cent, in the first three days, but after the hipse of about 

 a Aveelv the survivors appeared to be fully acclimatised to the 

 changed conditions, and often remained healthy for some 

 months. 



Experiments on animals whose health was doubtful were 

 of no value, both because the shock consequent on the 

 injection of the foreign body frequently caused death, and 

 also because the reaction of the tissues was not normal in 

 unhealthy specimens. When a Pecten is healthy it lies 

 with the valves of the shell slightly apart, the tentacles are 

 expanded, and it responds rapidly to any stimulus by closing 

 the shell; when held up in the air, the water which drains 

 away is clear and contains no slime. An unhealthy specimen 

 lies with the valves of the shell wide open, there is little or 

 no response to stimuli, and the valves only close under 

 pressure. The tentacles are retracted, and the gonads, gills, 

 and tissues generally, look Habby and unhealthy. The water 

 which flows out between the valves is slimy and viscid, and 

 this is generally the first sign of deterioration. 



All instruments used in the experiments were carefully 

 sterilised in boiling water. 



The transplanting needle resembles a large hypodermic 

 needle about 1 mm. in diameter and 6 cm. lono-. Into the 

 hollow needle a somewhat longer stylet fits closely and Avorks 

 like a piston. Any material taken up in the point of the 

 needle is sucked in by drawing the stylet back, and again 

 ejected by pushing it forwai-d. 



For injecting into the muscle, a solution of agar in sea- 

 watei", coloured by a little heematein, was used. The agar jelly 

 was liquefied by heating in boiling water, and was drawn up 

 into the transplantation needle. On cooling it forms a 

 cylinder, of the diameter of the needle, which is easily intro- 

 duced into the nniscle. 



The adductor muscle of Pecten maxinius is so large that 

 there is no difficuly in selecting a spot at which to bore the 

 shell. The apex of an equilateral triangle, having for its 

 base the line of junction of the posterior auricula with the 



VOL. 55, PART 3. NEW SERIES. 39 



