34 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Coelentera. 



Rheotropism of Hydroids.* — P. Hallez has shown that Bougain- 

 villea ramosa Van Beneden, grown in troubled waters, develops a large 

 number of stolons and takes on an appearance very different from the 

 normal, so different that it has been described as a separate species, 

 B. fruticosa Allman. He has also experimented with Eudendrium and 

 Halecium, and the result of reaction to the movements of the water (the 

 rheotropic reaction) is especially an excessive development of stolons 

 which serve to consolidate the colony. But though this proliferation of 

 the stolon system changes the appearance of the colony, it is not more 

 than a secondary effect. 



New Pelagic Coelenterate.t — C. Dawydoff describes Hydroctena 

 salensTcii g. et sp. n., three species of which he found at the Moluccas. In 

 its umbrella, velum, manubrium, and some other features it resembles 

 a craspedote medusoid, but in its aboral sensitive organ, its tentacular 

 apparatus, and in some details of its gastrovascular system (e.g. an axial 

 unpaired canal towards the aboral pole, two special lateral or tentacular 

 canals) it suggests the Ctenophora. The author's general view of the 

 affinities of his new type may be indicated in this scheme : 



/ Hydroctena Ctenophora 



Hydromedusse (especially / 

 Narcomedusse). \ 



^Ctenoplana — Cceloplana — Turbellaria 



Spicule Formation in Alcyonium.J — W. Woodland finds that a 

 spicule first appears in the cytoplasm of a scleroblast as a small spherical 

 concretion, and remains approximately spherical until the division into 

 two of the nucleus. It then becomes somewhat dumb-bell like, and the 

 two nuclei usually travel to its opposite ends. In the next stage it 

 somewhat resembles a caudal vertebra, and like preceding and succeeding 

 stages is enclosed in a granular protoplasmic sheath containing two 

 nuclei, which are usually situated at the extremities. As to the various 

 forms of adult Alcyonarian spicules, the author makes two suggestions. 

 Growing spicules situated in a mass of mesoglceal substance far removed 

 from any limiting surface must, owing to the proximity of other spicules, 

 endodermal canals, and other heterogeneities of constitution of the sur- 

 rounding medium, necessarily be subject to an aggregate of influences 

 which tend to produce irregularity of form ; and the second is that the 

 extension of a growing body into a surrounding resistant medium is 

 most easily effected by the protrusion of more or less acute processes 

 which, in virtue of their acuteness, are best able to cleave a passage. 



Porifera. 



Oscules of Cinachyra.§ — R. Kirkpatrick has some notes on this 

 genus of Tetractinellids, with especial reference to G. barbata Sollass 

 specimens of which were obtained by the ' Discovery ' from the Antarctic. 



* Comptes Rendus, cxli. (1905) pp. 727-30. 



t Mem. Acad. Imp. Sci. St. Petersbourg, xiv. (1903, received 1905) pp. 1-16 (1 pi.) 



% Quart. Joum. Micr. Sci., xlix. (1905) pp. 283-304 (2 pis. and 2 figs.). 



§ Ann. Nat. Hist., xvi. (1905) pp. 662-7 (1 pi.). 



