6 THE ZOOLOGIST. 



arrangement. Again, the duration of the life of the stocks from 

 which the buds issue is an important point, because it is possible 

 that some may be annual, as in the case of Gonothyroea Loveni on 

 the Mussels of the Eden, and as likewise occurs in the fresh- 

 water Polyzoa. The budding of the somatic cells of the organism 

 therefore would not alone suffice to preserve the species, and 

 hence the necessity for a method resulting in the development of 

 a pelagic medusa in which the eggs are produced, and, more- 

 over, carried throughout the ocean to new sites by its intrinsic 

 swimming powers and the effects of currents. 

 | In connection with the budding and branching of zoophytes, 

 some very interesting observations have recently been made by 

 Jaques Loeb.* It is known that the growth of zoophytes takes 

 place according to certain definite laws, the inferior end sending off 

 root-like processes, while the upper continues the axis, and gives 

 off branches with the cups for the polypites. Loeb found that 

 if the zoophyte (Antennularia) is suspended in sea-water upside 

 down the lower end (now the upper) gives off branches with the 

 polypites on the upper side, while the former upper end gives off 

 roots. If placed horizontally, the branches on the lower side 

 grow vertically downwards in the form of root-like processes, 

 which fix themselves to the surface of the glass (geotropic). The 

 branches on the upper side either perish or produce long slender 

 perfectly straight stems, which grow vertically upwards. At 

 parts of the upper surface of the main axis, however, new stems 

 grow vertically upward, and give off typical little branches with 

 polyps. If placed obliquely with the normal upper end highest 

 a new stem arises from the apex, and roots from the lower end, 

 while if inverted the same thing happens. Gravitation thus 

 appears to determine the place of origin of organs. In fragments 

 of Margelis {Bougainvillea) all the stems which touch the glass 

 give rise to roots, the free parts giving origin to polypites. 

 Contact with a solid body thus plays the same role as gravitation 

 does in Antennularia. In Pennaria he produced roots at both 

 ends of a small stem that bore no polyps. If a solid body be 

 brought into contact with it, it begins to grow away from it, and 

 the new stem is soon nearly perpendicular to the surface. The 

 foregoing manifestations are called by Loeb " Heteromorphism." 



:;: Biol. Lect., "Woods Hall, 1894, p. 37 et seq. 



