44 



NA TURE 



[November io, i< 



ON KEEPING MEDUSAE AND OTHER FREE- 

 SWIMMING MARINE ANIMALS ALIVE 

 IN SMALL AQUARIA. 

 A LTHOL'dll many marine animals, more especially tliose 

 "'^ which live between tide-marks, or in shallow water near 

 'he shnre, can without great difficulty be kept in a healthy stale 

 in confinement, this is by no means the case with those in- 

 vertebrates whose natural habit is to swim freely in the sea, and 

 previous attempts to rear pelagic larvae to the adult stage have 

 only rarely been attended with much success. A method of 

 overcoming some of these difficulties, which should prove of 

 considerable use to marine naturalists, has recently been in use 

 at the Plymouth Laboratory, and is described by Mr. E. T. 

 Browne in the Journal of the Marine Biological Association 

 (vol. V. Xo. 2). 



Mr. Browne arrived at the idea of the apparatus as the result 

 of repeated attempts to keep medusae alive in confinement. It 

 was noticed that when recently captured medusae were put into 

 clean sea-vvater, though they at first swam vigorously about, 

 hey invariably became sluggish in the course of a few hour-s 



even if the water were constanlly changed, settled tuihe bottom 

 and finally died. When watching medusae in the sea it was 

 observed that they simply float along with the tide without often 

 pulsating the umbrella. It was therefore thought that if a 

 movement in the water of anaquariiuii could be obtained, which 

 would keep the medusae const.mtly floating about independently 

 of_ their own pulsation, better results might be obtained ; and 

 this has proved to be the case. A suitable movement of the 

 water can be conveniently brought about by means of a glass 

 plate made to rise and fall slowly through tlie water. 



A motion of this kind can be arranged in many different ways, 

 the apparatus, illustrated in Fig. i, being the form originally de- 

 signed by Mr. Browne in conjunction with the Director of the 

 Plymouth Laboratory, which has now been continuously working 

 for a year. The sea water, obtained from the open sea at some 

 distance from shore, is contained in a glass bell-jar of about 10 | 

 gallons capacity, provided with a wooden cover made in two 

 halves. A glass plate is suspended in the water by means of a 

 glass rod passing through a hole in its centre, the other end o( 

 the rod being attached to one end of a light wooden beam. This 

 beam works on a hinge at the centre, and from its other end a 

 small tin bucket is hung. The bucket is fitted with a self-empty- j 

 ing siphon, and is supplied with a slight stream of water by [ 



NO. 15 I 5, VOL. 59] 



means of a rubber tube attached to the fresh- water supply. The 

 weights of the bucket and glass plate are so adjusted that the 

 plate moves up and down in the sea-water as the bucket 

 alternately fills and empties. Extra weight is added when 

 required by placing shot in a small bottle hung at one end of 

 the beam. In this way a delicate adjustment can be m.idc. and 

 the plate caused to travel as slowly as is desired. The length 

 of the .stroke is regulated by two stops, and a slit in the covet 

 of the bell-jar, through which the gla.ss rod passes, prevents the 

 plate from striking the sides of the jar. 



Arrangements have since been made in the laboratory, 1 

 which a large number of glass plates, or " plungers '" ns ih. 

 have been named, can be worked in a similar way. A modifu 

 form of the apparatus, in which the glass plate is replaced by a 

 glass funnel with a small hole in its top, has also been used with 

 advantage. The funnel is fixed so that it is brought out of thi 

 wa er by the upward stroke of the plunger. At each down 

 ward stroke it carries with it a funnel-full of air, which escapi 

 by way of the hole, and bubbles through the water. 



Amongst the nifdusae which were successfully kept in the 

 bell-jar were Phiulidiuiii hiiskianutii, which grew and developed 

 fresh tentacles, P/iiaiiJiiini cym- 

 haloidcitm, which in twenty-five 

 days added five new tentacles 

 and five marginal bulbs, and a 

 -; _ri( - of Margt'lis, which in 

 en days added two new 

 < in each of the four 

 ni.iii;u.al groups, and the oral 

 tentacles twice dichotomously 

 divided. Two medusae of C/ado- 

 tu-fna yadiatitnt were pl.\ced in 

 the same bell-jar in the sum 

 nicr of 1S97, and in the follow 

 ing spring several colonies lii 

 the hydroid of this specii- 

 appeared. During the preseii 

 summer (189S) lhe.se colonic 

 have freely budded off medusae 

 several hundreds being seen i: 

 the bell-jar at one time. 



Crustacean, annelid and mol 

 luscan larvae were put into tli 

 bell-jar from time to time (tu 

 gether with Copepods), as fon 

 fur the medus.ae. Many of th 

 larvae, which escaped captuti 

 by the medusae, continued to 

 develop and attained the adult 

 form. Amongst these were 

 Cluuloflcrus variopedatiis (tKe 

 tube of an adult worm froki 

 an 1S97 larva being about foMr 

 inches long in June if " 

 C a pi I el la t:apilala, PolyniK sp., 

 JVil:a edttlis, Porlnntis sp. , as 

 well as small (lasteropods. 

 Hermit-crabs, and Barnacltt. 

 Colonies o. hydroids were also found to flourish well when 

 kept in similar aquaria and plentifully supplied with Copepods, 

 which they capture and devour in large numbers. E. |. .\. 



PHYSICS A T THE AMERICAN ASSOC I A TION 

 'T'HE Physics .Section (Section B) of the .-\merican .■Vsso 

 •^ tion was organised with \'ice- President Prof. E. P. Whj 

 man in the chair. His vice-presidential address, on cola 

 vision, printed in the issue of Science for September 9, 

 well received, and constitutes a valuable ;-,■>««/(' of the subject 



The programme of the Section included titles of fifty pap 

 of which forty were read. Many of these papers were of a v^ 

 high order, and almo.st every one of them was creditable 

 interesting. Brief abstracts of some of them are subjoined. 



" .'\ redetermination of the ampere," undertaken, unde^4 

 grant from the Association, by Prof. G. \V. Patterson and MtJ 

 Karl E. Guthe, of Ann Arbor. This work, for which 

 accuracy of about one part in Sooo is claimed, gives oooiltf)^ 

 grammes for the electro-chemical equivalent of silver, tiA 

 reconciles almost exactly the mechanical equivalent of heat aJ 

 obtained iiy electrical methods with Prof. Rowland's correcieq 



