42 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Stylasterids.* — Hjahnar Broch deals in a very careful manner with 

 northern Stylasterids : 1'lwbnlhrns symmetricus ; Stylaster gemmascens 

 and Stylaster roseas, both of which he includes .in a new subgenus 

 Eustyhtxtrr -. and Stylaster norvegicus, which he refers in the subgenus 

 AJlopora. The structure of these four forms is discussed and finely 

 illustrated. A consideration of affinities leads him to the conclusion 

 that the Hydroeorallines are two convergent families of Hydroids, 

 marked by their calcareous skeleton and dimorphism. The family 

 Milleporidaj probably had its origin from the Corynidre and the Stylas- 

 terids from the Bouganvilliidas. Broch calls attention to the interesting 

 fact that as in many other ( Vlenterates, so in the four northern Stylas- 

 terids, the skeleton is formed of Aragonite. As all Aragonite contains 

 magnesium, this means that the animals have the power to make use of 

 the magnesium in the sea water. But why some corals should have 

 aragonite skeletons and others (like Corallium, Tubipora, Cystvphyllvm, 

 and Anabacia) should have calcite skeletons remains quite obscure. 



Hydroids of the Great Australian Bight.f— W. M. Bale describes 

 some new species, e.g. of Gryptolaria, Hypopyxis, and Nemertesia. As in 

 a former report, the Plumularians predominate, and are of interest as 

 including types of Aglaoph&nia and Halicornaria not previously known 



from Australian localities. 



Restitution Masses formed by the Dissociated Cells of Hydroids. i 

 W. de Morgan and G. H. Drew have made a study of the restitution 

 masses formed by the dissociated cells of the Hydroids Antentoularia 

 ramosa and A . antennina Their results largely bear out those obtained 

 by H. Y. Wilson, but the histological structure of the restitution masses 

 differed in many ways from that described by Wilson. The Hydroids 

 were cut in pieces and pressed through bolting silk, with the result that 

 isolated cells and small cell-aggregates were obtained, which soon aggre- 

 gated together to form compact masses. These restitution masses 

 secreted a perisarc within from 12 to IX hours. Various changes in 

 shape, and general retraction of the mass away from the perisarc 

 occurred later, but even up to sixty days there was no sign of the 

 regeneration of the hydranths. The restitution masses consisted of 

 ectoderm and endoderm cells, and in addition such structures as nemato- 

 cysts, ova and broken-down cells, all of which were subsequently 

 absorbed, and played no part in the future development. The ectoderm 

 cells were relatively little damaged, and were embedded in a plasmodial 

 mass formed by the endoderm cells. A definite layer of ectoderm cells 

 is formed on the surface, and these cells secrete the perisarc. Gradual 

 aggregation and segregation of the endoderm cells from the plasmodial 

 mass takes place ; and they form very definite tubules, very similar in 

 structure to the ccenosarcal tubules continuous with the enteric cavities 

 of the normal hydranths. These tubules are embedded in a mass of 

 ectoderm cells ; they are convoluted and ramify in all directions. Many 



* Danish Ingolf Exped., v. (1914) pp. 1-25 (5 pis. and 6 figs.). 



t Biol. Results Fishing Experiments Australia, ii. (1914) pp. 166-88 (4 pis.). 



J Journ. Marine Biol. Assoc, x. (1914) pp. 440-63. 





