352 L. MURBACH. 



they may develop directly into polyps. The processes con- 

 stricted off at the basal end of Corymorpha, which, according 

 to Allman/ develop into new polyps, if not the remnants 

 of a Hydrorhiza might correctly be compared with the blasto- 

 lytes. 



Nearest of all, perhaps, comes the asexual reproduction of 

 Protohydra, L., recently more fully investigated by Chun.^ 

 But this polyp is more primitive, and fission takes place at 

 almost any point on the body, the fission zone not being 

 constant as it is in Hypolytus. 



Normal asexual reproduction in Hypolytus by spontaneous 

 fission of a definite portion of the free foot end is unlike any 

 reproductive process heretofore described among Hydrozoa, and 

 since it precludes an attached condition it probably represents 

 an ancestral mode retained by this form. It may have gone 

 through some such stage as Protohydra now does. 



The modification of the normal process described under 

 asexual reproduction remains unexplained, and I offer the 

 following as a possible one. It would be of great advantage to 

 the young polyp to have the organs for obtaining a livelihood 

 developed as early as possible. If, now, the material from 

 which the hydranth and the tentacles are to be developed can 

 be accumulated and differentiated (the lateral enlargement) 

 while constriction and fission are going on, the young polyp at 

 the close of this operation could the sooner be ready for the 

 activities of life. This involves formation of a hydranth from 

 a lateral portion of the hydrocaulus instead of from the axial ; 

 in fact, just what does take place in Hypolytus. It furthermore 

 suggests a possible explanation of the origin of lateral budding 

 among marine hydroids, by assuming that the precocious 

 development of a hydranth made the separation from the 

 parent unnecessary. 



To account for the unattached condition of Hypolytus we 

 may assume that it is secondary, or, on the other hand, that it 



^ 'A Monograph of Gymnoblaslic or Tubularian Hydroids,' 1871-2. 

 2 Cliun, Carl, 'Bronu's Klassen u. Ordnungen d. Thierreichs,' Bd. ii, 

 p. 115. 



