SUMMARY OF CURRENT RESEARCHES RELATING TO 
62 
pattern of the cercaria is likewise found in the sporocyst. The data have 
a bearing on the application of mathematics to the problems of growth 
and development. There is a fundamental pattern potentially inherent 
in the protoplasm. J. A. T. 
Ccelentera. 
Polarity in Obelia. — E. J. Lund ( Journ . Exper. Zool., 1921, 34, 
471-93, 3 pis., 3 figs.). A study of the effects of electric currents on 
regenerating internodes of Obelia commissuralis. Cut-off intern odes possess 
and retain an inherent polarity, according to which the regeneration of a 
hydranth occurs at the apical end before that at the basal end. Apical 
internodes develop hydranth s earlier than internodes of basal origin. 
With an appropriate density of electric current all hydranth formation 
on ends of internodes when turned towards the cathode can be delayed 
or entirely inhibited, while at the same time hydranths may form in a 
high percentage of pieces on ends pointed toward the anode. In the 
same conditions stolons may regenerate and function normally on ends 
toward the cathode. These two statements hold for pieces irrespectively 
of whether the basal or the apical end of an internode is pointed toward 
the anode. That is, the inherent normal polarity of the internode may 
be reversed by means of an electric current. A current density barely 
able to inhibit regeneration in basal internodes cannot inhibit regenera- 
tion in apical internodes of the same branch. The establishment of an 
electrochemical polarity is probably a primary, fundamentally associated 
condition for the development of morphological polarity, for it has been 
shown that the physiological mechanism which determines morphological 
polarity can be controlled and directed by an electric current of external 
origin. J. A. T. 
Plumularidse of Hirondelle and Princess Alice. — Maurice Bedot 
( Resultats Campagnes Scientifiques de Monaco , 1921, 60 , 1-72, 6 pis.). 
An account of new species of Polyplumaria , Halicornaria , and Glado- 
carpus , and fresh information about many other Plumularids. He also 
discusses a number of genera, much multiplied of recent years, in the 
sub-family Eleutheropleinae, e.g. Thecocaulus and Schizotricha. 
J. A. T. 
Green Hydra fusca. — W.Goetsch {Zool. Anzeig., 1921, 53, 173-6). 
Beport of a stock of brown Hydra whicLi exhibited a temporary infection 
with green algae. The infected forms belonged to Schulze’s proposed 
genus Pelmatohydra, and it may be said that symbiosis does not occur 
in this group. But the genus “ Hydra, ” which remains after 
separating off the stalked Pelmatohydra and Hydra viridis (now called 
Ghloro hydra), may show in a culture a lasting symbiosis with algae, and 
Goetsch also reports on this. The infection with Chlorella sp. may be 
effected with the aid of Daphnids. A constant expulsion of algae was 
observed. The symbiosis observed was not seen in natural conditions ; 
it occurred in laboratory aquaria. J. A. T. 
Revision of Genus Plexaura.— Johannes Moser {Zool. Anzeig., 
1921, 53, 110-18). A useful revision of this Alcyonarian genus, which 
is restricted to the littoral region of the Tropical West Atlantic. A 
