47 



As further instances of the group K we may mention from the 

 same family of creatures: Actinomma drymodes, and Asteracan- 

 thion, after Haeckel's descriptions; of the group P: Aulosphaera 

 icosahedra in its youthforms; etc. 



In the vegetable world a certain number of pollen-cells seem to 

 belong to these symmetry-classes: to group T those of Corydalis 

 sempervirens] and 

 to group P the 



pollen-cells of 

 Buchholzia mari- 

 tima, Fumaria 

 spicata, Polygo- 

 num amphibium, 

 Rivina brasilien- 

 sis, Bannisteria 

 versicolor, etc. The 

 number of these 



examples can 

 certainly be aug- 

 mented. Some of 

 these pollen-cells 

 are reproduced in 



Fig. 51. 



Pollen-cells of 



Dianthus Cartusianorum ( 1 ). Luzula campestris ( 4 ) 



/*& 5* Circaea alpina ( 2 ). Mastixea arborea (i) 



11. As has Rivina humilis L. ( 3 ). 



been repeatedly 



stated, all forms and objects which show the symmetry of any 

 of these -groups possessing only axes of the first order, are diffe- 

 rent from their mirror- 

 images. Of course all these 

 stereometrical figures and 

 objects lack an inversion- 

 centre, or, as is commonly 

 said, they do not possess a 

 "symmetry-centre" x ). This 

 is a fact of importance 



Fig. 52. 

 Right-, and left-handed 

 deltoid-dodecahedron. 



with respect to some phy- 

 sical properties, e. g., in 



x ) It may be remarked that the reverse of this conclusion is not generally 

 true: from the absence of a symmetry-centre, enantiomorphism does not 

 follow necessarily. 



