ANEMONES 4O5 



mesenteries. This assumption may gain in probability if the remark- 

 able correlation of siphonoglyphs and directives is remembered, for an 

 explanation of which we are equally at a loss. 



The regular hexamerous diglyphic polyps must be relatively more 

 numerous among the sexually than among the non-sexually produced 

 polyps. This is because basal fragmentation is responsible for an 

 important number of aberrant forms which must lessen the proportion 

 of regular hexamerous diglyphic polyps among the non-sexually pro- 

 duced polyps. The portion of regular hexamerous polyps which are 

 produced sexually to those w'hich arise non-sexually cannot be stated at 

 present. 



Having given reasons for believing that regular hexamerous polyps 

 develop non-sexually as well as sexually, it remains to consider whether 

 monoglyphic polyps develop sexually as wxll as non-sexually. 



There is no direct evidence for an affii-mative view. If we assume, 

 however, that buds tend to reproduce the structural type of the parent, 

 and remember that polyps with either one or two siphonoglyphs arise 

 non-sexually, the probabilities are very great that both monoglyphic 

 and diglyphic polpys are produced sexually. The same causes that 

 operate to produce a variation in the number of sijohonoglyphs of the 

 bud must also operate to produce a similar variation in the egg embryo. 

 Since the ancestral type is hexamerous, it is safe to assume that this 

 monoglyphic sexual type will be associated with hexamerous polyps. 

 At least until the complete development is known we shall be unable 

 to assert that irregularities in the mesenterial formula do not occur in 

 the polyps which are sexually produced. That such irregularities 

 may occur in the latter is suggested by the development of perfect 

 mesenteries in polyps which have arisen by fission. As the fission 

 plane separates the directives of the siphonoglyph through w'hich it 

 passes, a new directive must be developed for each individual. Often 

 other perfect mesenteries arise between the separating oesophagi. It 

 is clear that at least under the conditions which make fission possible 

 new perfect mesenteries may be developed in sexually mature polyps. 



In the foregoing discussion I have attempted to show : 



(a) That regular hexamerous diglyphic polyps arise non-sexually as 

 well as sexually ; 



(6) That monoglyphic polyps arise sexually as well as non-sex- 

 ually ; 



(c) That irregularities in the number and arrangement of me- 

 senteries may be accounted for largely, perhaps exclusively, by non- 

 sexual reproduction (mainly basal fragmentation) ; 

 Proc. Wash. Acad. Sci., August, 1902. 



