36 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Plankton of Attersee. * —Dr. Carl v. Keissler gives a list of the 

 organisms of this Upper Austrian lake during the month of August 1900, 

 together with some critical remarks. The nettings at a depth of 20-30 

 metres showed a smaller amount of plankton than that present at the 

 same depths in the North German lakes, but greater than that of the 

 large Alpine lakes, e.g. the Neueuberger See. Just as in the Alpine 

 lakes, the upper layers of water showed a small volume of plankton ; for 

 not till a depth of five metres was reached was any considerable amount 

 ohtained. But as also occurs elsewhere, the organisms rise to the surface 

 in the evenings, and then the layers from 0-5 metres and from 2-5 metres 

 contain three to four times the plankton volume which they possess by 



day. 



The same author f gives an account of the contents of two tow-nettings 

 made in April in the Aber or Wolfgang Lake in Salzburg. The most 

 numerous animals were Crustacean larva} and DiajAomus graciloides. 

 Eotifers were remarkable for their absence. 



INVERTEBRATA. 

 Mollusca. 

 o. Cephalopoda. 



Notes on Living Nautilus.! — Prof. Bashford Dean has studied 

 Nautilus in the region of southern Negros (Philippines), where it is 

 collected by the fishermen in fish-cages. 



There are often visible sexual differences in the shells, that of the 

 female bein<* wider at the sides of the oral aperture and with a somewhat 

 angular contour. But this test is not always applicable. Irregular, 

 sometimes undulating, lines of growth on the shell may be seen, some- 

 times several on the wall of a single chamber. In captivity the animal 

 often rests quietly for hours, with its face and exposed parts a clean 

 opaque white, like the shell ; the dorsal surface of the hood, which is 

 brownish, is almost the only area of pigmentation. They died in less 

 than a day in captivity, but retain a life-like position after death. One 

 dead one was seen to float on the surface. The appearance of the animal 

 when resting and when retracting is carefully described. 



The author notes the mobility of the tentacles, their great possibilities 

 of extension and retraction, and suggests that the lengthening and 

 shortening may be connected with the transverse foldings which enable 

 the tentacles to serve as adhesive organs. There can be little doubt that 

 the Nautilus is naturally very active ; it will suddenly sweep from the 

 bottom and bump into a corner with some force, rising usually not more 

 than three or four inches off the ground ; rotation (turning to right or 

 left) is readily accomplished ; a curious rocking movement is common. 



A fisherman's uninspired description of what may have been the 

 deposited eggs is given. 



Development of Radula in Cephalopoda.§— G. Eottmann, who has 

 chiefly employed Loligo vulgaris as material, finds that the radular sac 



* Verhaudl. k. k. Zool.-bot. Ges. Wien, li. (1901) pp. 392-401 (2 figs.). 



t Tom. cit., pp. 401-4. J Araer. Nat, xxxv. (1901) pp. S1S-37 (15 figs.). 



§ Zeitschr. wiss. Zool., lxx. (1901) pp. 236-62 [2 pis.). 



