20 PLANT-ANIMALS [CH. 



prone on the soft, grey ooze of the sea-floor. The 

 extremities of the Ascophyllum are clothed with tufts 

 of fine, epiphytic brown and red sea-weeds. Further 

 out, as the tide continues to fall, the browner weeds 

 are becoming uncovered ; first, the dichotomous straps 

 of Himanthalia which spring from button or saucer- 

 like stalks attached to the rocks, and then the finger- 

 like Pycnophycus (Fig. 2) which extends beyond the 

 seaward limits of even the biggest spring tides. It is 

 among the fine weeds attached to Pycnophycus that 

 C. paradoxa is to be found. On dangling these weeds 

 in water, the animals come out, but as single spies 

 not in battalions like C. roscoflensis which lies in 

 swarms thirty yards further up the beach. The 

 abode of C. paradoxa is less circumscribed than that 

 of C. roscoffensis and shifts with the tides. At the 

 onset of the spring tides, minute specimens may be 

 taken from among the epiphytic weeds attached to 

 the most landward of the brown sea-Aveeds (Fucus). 

 During subsequent spring tides, the animals must be 

 sought lower down the beach in the zone occupied 

 by Himanthalia and Ascophyllum ; whilst, yet later 

 in the same series of spring tides, C. paradoxa is to 

 be found only in the Pycnophycus zone. Just where 

 that dark brown weed ceases to be exposed at low 

 water of the largest spring tides is the further limit 

 of the paradoxa zone (Fig. 7). Like the Greek sailors 

 described in Eothcn C. paradoxa hugs the shore. Ex- 



