728 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Tetraplatia.* — Albert Niedermayer discusses the position of this 

 enigmatical Ccelenterate, which was first described by Busch in 1851. 

 It is a small whitish animal, 1-5 mm. in length, covered with ciliated 

 epithelium, and in shape like two four-sided pyramids united base to 

 base. There seems to be much in favour of Carlgren's view that the 

 creature is a divergent Hydromedusoid, requiring a special family, 

 Pteromednsa3, between Trachomedusse and Narcornedusas. Among the 

 important features may be noted : the double wing-like lappets, the 

 ex-umbrellar musculature, the motor-cells in place of sub-umbrellar 

 musculature, the invagination of the gonads into the gastral cavity, the 

 expansion of the manubrium, and the closing-off of the endodermal 

 " auditory organ " by a velar vesicle. The single genus Tetraplatia is 

 represented by two species, T. chain' Carlgren, 1909, and T. volitans 

 Busch, 1851. 



Pofifera. 



Nature of Astrosclera.t — W. Weltner discusses the nature of the 

 remarkable sponge which Lister described as Astrosclera willeyana, and 

 regarded as a very divergent type of Calcarea. Weltner will not admit 

 its position among the Calcarea, but regards it as an Ectyonine siliceous 

 sponge. The calcareous sclerites which occur along with the siliceous 

 sclerites belong to the basal part of a stone-coral on which Astrosclera is 

 growing. This, at all events, is "Weltner's re-interpretation of the facts. 



Protozoa. 



Nucleus of Amoebse.ij: — E. Chatton has made a study of the nucleus 

 in various types of Amoeba. In its simplest expression, Amceba3 of the 

 Umax type, the nucleus includes : (1) a caryosome formed of a funda- 

 mental substance (plastin), impregnated with chromatin, and containing 

 a centriole ; (2) a nuclear sap, more or less charged with a chromatin 

 substance (identical with or very similar to that of the caryosome), 

 and with an achromatin substance (linin) ; and (3) of a membrane, in 

 most cases ill-defined. Such a nucleus is of the " protokaryon " type, 

 and its division has been called by Nagler " promitosis." In more 

 evolved types the elements and substances primitively condensed in the 

 caryosome are separated out, and the division is a more complex " nieso- 

 mitosis " or " metamitosis." The author recognizes three chief stages in 

 the differentiation of the nuclear apparatus, and three forms of division 

 (named above) corresponding to these. 



Parasites of Labridse.i — E. Chatton describes Amoeba mucicola 

 Chatton and Trichodina labrorum sp. 11. from the gills of Symphodus, 

 where they are associated with epidemic disease, the Trichodina probably 

 preparing the way for the Amccba. The author gives a detailed account, 

 of the minute structure of Amccba mucicola and of its nuclear division. 

 In an appendix he calls attention to an interesting point, that some 



* Verh. Zool. Bot. Ges. Wien, lx. (1910) pp. 5S-73 (3 figs.). 



t Arcbiv Naturges., lxxvi. (1910) pp. 128-34. 



% Arch. Zool. Exp6r., v. (1910) pp. 267-337 (13 figs.). 



§ Tom. cit., pp. 239-66 (1 pi.). 



