66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



variation of this Rotifer, in which he showed how the variations could 

 be traced in three or four definite directions from the type species, so as 

 to embrace all the known varieties of this very variable form. The 

 second part, now published, is an elaborate account of the conditions 

 which appear to produce these variations. These conditions the author 

 finds principally in the constitution of the water of the various ponds 

 and lakes, and in the changes of temperature due to the seasons. By 

 collecting regularly once a month throughout the year in seven different 

 localities, examining and measuring twenty-five to fifty specimens each 

 time, and tabulating the results, the author has ascertained that Anurcea 

 cochlearis goes through a regular cycle of variation, which is repeated 

 every year.' During the cold season — December, January, and February 

 —this species is represented in the old bed of the Rhine, near Neuhofen, 

 by the typical form and by the variety macraccmtha, with long posterior 

 spine. In the spring these forms are very gradually replaced by members 

 of the irregularis and hispida series, with short spines, including tecta, 

 with no spine ; so that by the month of May the long-spined varieties 

 have entirely disappeared, to reappear again in the month of October 

 or November. The author has observed the same regular cycle of 

 variation in the same locality for a period of twelve years. In order to 

 account for these regular variations, the author is inclined to adopt 

 W. Oswald's suggestion that the reason is to be found mainly in the 

 " internal friction " of the water, which varies very considerably with 

 the temperature, and which must have an influence on the floating 

 capacity of the various organisms living in the water. He thus sets 

 aside as insufficient the theory advanced by Wesenberg-Lund, who thinks 

 that similar seasonal changes in the size of animals and appendages in 

 Cladocera, Rotif era and Infusoria, are due to a tendency to accommodate 

 the organisms to changes in the specific gravity of fresh water, which 

 decreases, but only slightly, with increasing temperature. 



New Rotifers.* — E. von Daday gives an account of the Plankton 

 organisms collected by Franz Werner in some fresh-water lakes in the 

 northern parts of Asia Minor, and thereby figures and describes one new 

 species and one new variety of Rotifers, Mastigocerca heterostyla (which 

 really is Rattulus bicornis of Western) and Brachionus rubens var. 

 Wern&ri. The author also gives some new figures of several species 

 already known, namely Brachionus budapestinensis and forficula and 

 Notops macro urus . 



Echinoderma. 



Non-regeneration of Sphaeridia in Sea-Urchins. f — Yves Delage 

 in an interesting note points out that removal of the epidermis, spines, 

 pedicellariae, sphaeridia,— everything in fact — from the surface of Para- 

 centrotus (Stryonglocentrotus) Hindus, was followed by regeneration of 

 all the structures, except the sphaeridia. It does not appear to be the 

 case that these bodies are necessary to equilibrium as has been suggested, 

 since the urchins can turn over, although these have been removed. 



Osmotic Action of the Internal Fluids of EchinodermsJ — V. Henri 

 and S. Lalou find that the membranes connecting the internal cavity of 



* SB. K. Acad. \Vi>s. Wien, Bd. cxii. pp. 139-07(1 pi.). 

 t Coiuptes Rendus, cxxxvii. (1903) pp. 681-2. 

 j Tom. cit, pp. 721-3. 



