386 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Triclads from Inle Lake. — Tokio Kaburaki {Records Indian 

 Museum, 1918, 14, 187-94, 1 pL). Three new species of Planaria are 

 established, and the reproductive system in particular is described in 

 considerable detail. J. A. T. 



Echinoderma. 



Experiments with Larval Echinoids. — E. W. Macbride {Proc. 

 Roy. Soc, 1918, B., 90, 323-48, 7 pis., 5 figs.). If the larvae of 

 Echinus miliaris be exposed to the action of hypertonic sea-water for a 

 week commencing with the fourth day of development, many of them 

 will develop on the right side as well as on the left a hydrocoele or 

 water-vascular rudiment. In connexion with this second hydrocoele all 

 the structures which normally develop in connexion with the left 

 hydrocoele may make their appearance, viz. spines, tentacles and dental 

 sacs. If the larvas be starved during the first week of their existence 

 and then placed in favourable conditions as regards food and space, 

 they will continue their development, but many of them will be devoid 

 of both pedicellariffi and hydrocoele, and will have in place of both a 

 group of pointed spines on each side. Such larvse will, in the majority 

 of cases, be devoid of madreporic pore and axial sinus, but will possess 

 ,a well-developed madreporic vesicle. 



As hypertonic sea-water may unloose the potentiality of an unfertilized 

 ovum and lead to development, it is probable that the formation of a 

 right hydrocoele in larvge exposed to hypertonic sea-water implies the 

 actualization of a potentiality which is normally in abeyance. The 

 probable Gephalodiscus-V\ke ancestor of Echinoderms may perhaps be 

 credited with the possession of two hydrocceles. In the proto-echinoderm 

 one hydroccfile alone persisted. It is suggested that a small area of the 

 ccelomic wall gave origin to the hydrocoele bud or buds, and that 

 hormones producing morphogenic modifications were stored in the 

 hydrocoele bud. " When this area under the influence of stimulation 

 produced two hydrocoeles instead of one, these hormones were shed 

 abroad on both sides of the larva, although they had only been evolved 

 in connexion with the left side. The body of an embryo is not, like a 

 picture puzzle, a mosaic of pieces each destined to form a particular 

 organ, but consists of sheets of indifferent material ' without form or 

 void ' on which a formative ' something ' works and evokes the 

 beautiful detail of the adult structure." J. A. T. 



Unstalked Crinoids of Siboga Expedition. — Austin H. Clark 

 (ResuUats Ezplor. Siboga, 1918, Monographic 421), ix + 1-300, 28 pi., 

 17 figs.). The collection made by the Siboga, at the Aru Islands, Sulu 

 Archipelago, etc., included 149 Comatulids, of which 64 were new. 

 Among the features of special interest may be noted : — A new type 

 (Atopocrinus) with five arms and no basals, extremely small species of 

 Monachocriniis and Bythocrinus ; a very large species of Democrinus ; a 

 new type of Atehcrinus, with short cirri and very large basals ; extremely 

 small species of Compsometra ; small species of Decametra ; Psathyrometra ; 

 a series of types from the warm, shallow and muddy Java Sea, which 

 are marked by long and slender long-segmented cirri ; the most ornate 



