156 



PEOr. ST. GEOEGE MIVAKT ON 



symmetrical, and complex forms cannot be due to the action of 

 natural selection, and sexual selection can of course take no part 

 in forming such organisms as these. We seem here to have forced 

 upon our notice the action of a kind of organic crystallization, 

 the expression of some as yet unknown law of animal organiza- 

 tion, here acting untrammelled by adaptive modifications or by 

 those needs which seem to be so readily responded to by the 

 wonderful plasticity of the animal world. 



Impressionahility, Locomotion, and Nutrition. 



The life-processes of the Eadiolaria are similar to and are 

 carried on by similar means as those which exist in the PolytTia- 

 lamia. Except in the existence of a central capsule and of yellow 

 cells (the nature of which is so doubtful), nothing in the shape of 

 organs is perceptible ; and the granules or other matter found 

 within the sarcode can circulate freely throughout its substance. 

 Yet there is some evidence that this structureless sarcode ministers 

 to a certain appreciation of light, since Professor Haeckel found 

 that in a few hours these organisms would cross and recross a 

 glass vessel in order apparently to reach its more illuminated side. 

 Possibly, however, as the Professor himself remarks, this move- 

 ment may have been really due to currents setting in towards the 

 warmer (which was of course the lighter) side of the vessel. 



Eadiolarians also seem sensible to heat, since in hot weather 

 they descend to cooler strata of the sea instead of remaining close 

 to the surface, as in weather less warm. They also show, as might 



Fig. 9. 



Thalassicolla nudeafa. A. Showing the alveoli expanded and the pseudopodia 

 protruded. B. Contracted. (After Hertwig.) 



be expected, sensibility to touch, in so far as they withdraw their 

 pseudopodia and contract their bodies upon the occurrence of any 



