SCIENCE- GOSSIP. 



345 



This interesting note called forth in the "English 

 Mechanic" the following letter, signed"C. F. R.,"in 

 which initials it is not difficult to recognise a well-known 

 authority on rotifers : — " Dr. Weir's note on the 

 remarkable sportive habits of Melicerta might be 

 supplemented with other more wondrous feats of this 

 wonderful rotiferon. Any one who has seen this help- 

 less, awkwardly swimming creature when it has had 

 the misfortune to become detached and to be driven 

 out of its tube will be much interested to hear that it 

 can dart about in and out of its house, hide behind 

 grains of sand with one eye over the edge or round 

 the corner, and do other frisky gambols. Dr. Weir 

 might well have added that, with a little perseverance 

 and a grain or two of imagination, Melicerta can be 

 seen to use its foot as a prehensile organ ; in fact, 

 like an elephant his nasal trunk. When a small 

 rotifer of the genus Rattphts or Mastigocerca comes 

 by, Melicerta will seize it, break off its long pointed 

 toe, and use it as a toothpick to clean its teeth, of 



the water. Boil therefore, for a short time, several 

 hundred cc. of water, and while this is still quite hot 

 pour it into a bottle with a tightly fitting stopper, 

 leaving little or no air between the water and the 

 stopper. When the water has become cooled to a 

 lukewarm temperature, place the objects in question 

 into the water and cork the bottle tightly as before. 

 After several hours (two or three to twenty-four 

 hours) the water will have absorbed all the gas, and 

 the object will have settled to the bottom. Should 

 the object still contain gas, repeat the operation. 

 Should one fear that the object may suffer injury, 

 normal salt solution, or alcohol, might be suggested. 

 Unfortunately, however, alcohol contains but little 

 gas in solution. 



New Cambridge Rocking Microtome. — The 

 Cambridge Scientific Company have recently brought 

 out a new and improved pattern of their well-known 

 rocking microtome. The earlier instrument was 



New Camukidge Rocking Microtome. 



which it has quite a number, quietly sitting the while 

 on the above-mentioned grain of sand. The eyesight 

 of Melicerta, with its vertebrate retina of rods and 

 cones, is so powerful that it often tries to look at the 

 observer through the other end of his (the observer's 

 own) microscope, and, no doubt, succeeds. A 

 wonderful creature is Melicerta, and, in order to 

 observe all these and other marvellous habits, a good 

 microscope and a little imagination only are required, 

 such as Dr. Weir seems to possess in so high a 

 degree. " 



Extracting Air from Microscope Objects. — 

 The following note, extracted from the "Optician," 

 may interest some of our readers : — One often finds, 

 after killing and hardening any small animal, that 

 some part of it, commonly the intestine, contains 

 air-bubbles. Also, in decalcifying small calcareous 

 animals with acids, especially when one hurries the 

 process, bubbles of CO., are not infrequently formed. 

 At all events, whatever the origin of the bubbles, 

 their presence is adverse to obtaining perfect sections 

 and series. Such bubbles of gas can be readily 

 removed by the following process, due to I'rofessor 

 E. W. Berger, of the Johns Hopkins University, 

 U.S.A. It is well known that water contains a con- 

 siderable quantity of air and some other gases in 

 solution, and that these can be removed by boiling 



introduced as far back as I Sc>5. and has made its way 

 into colleges and laboratories throughout '.lie world. 

 It is undoubtedly the simplest, cheapest, and mosl 

 efficient microtome for the cutting of serial sections. 

 It is unnecessary for us to describe the principle "I 

 this microtome, as we have already noticed the instru- 

 ment (Science-Gossip N.S., vol. ii. page 22S1 : but 



the improvements introduced in the new model are 

 increased rigidity, impossibility of making sections in 

 the upward movement, or of cutting thick and thin 

 sections, graduated arc for showing the thickness ol 

 the sections, catch for holding the object above the 

 razor edge, improved method of fixing the cord, and 

 new object-holder. The first three of these improve- 

 ments appear to us to be the most important, and to 

 have been successfullv accomplished. The price of 

 the microtome is slightly higher than hitherto, being 

 £4 I0.f., without razor and object-holder. There is 

 one drawback to the tise of a microtome of this type, 

 and that is that the cut surfaces have necessarily a 

 slight curve on them. In most cases this may be 

 ignored, but it is as well to mention here that another 

 pattern is made by the same firm, at a rather higher 

 price, by which entirely flat sections are cut. 

 Beginners may perhaps be reminded that a rocking 

 microtome is useful mainly for cutting long" ribbons " 

 of sections such as are used in biological and other 

 laboratories. 



