ORDER, DISORDER; TORSION, DETORSION 



59 



organism. In the gastropod Limnaea peregrea, the dextral 

 or sinistral torsion is controlled by a pair of allelomorphic 

 genes. In Focttingcria dextral and sinistral torsions do not 



Fig. 25. Foettingeria actiniarum: different aspects of the ciliary ?;ys- 

 tem. (a) Median protomont. (b) Last division, (c) Torsion of the 

 protomite. (d) Protomite. (e) Posterior pole of the protomite. (f) 

 Tomite. (g) Encysted phoront. The invaginated spiral coil has been 

 devaginated. (h) Young trophont. The torsion in the phoront (g) and 

 trophont (h) are inverse of the protomital torsion (e). 



reflect different genomes, but are the response to definite 

 phases of the life cycle. 



During the trophic phase, changes of the superficial archi- 

 tecture consist essentially in the unrolling of the kineto- 



