730 REPORT— 1895. 



maximum observed rate of exit per minute, multiplied by 20, gives a minimum 

 lower than the total number iu the nest. 



In some cases examined by the author the minimum was found to be very 

 much below the actual number. Thus a nest for which the observed maximum 

 average rate of issue was eleven per minute, was found — when the whole popula- 

 tion was killed and counted — to have contained, iu round numbers, 600. A nest 

 of which the maximum observed rate of issue was thirty per minute, was found to 

 have contained 1,600. 



SATURDAY, SEPTEMBER 14. 

 The Section did not meet. 



MONDAY, SEPTEMBER IG. 

 The following Papers were read : — 

 1. On Insect Transformations. By Professor L. C. Miall, F.R.S. 



2. On Mounting Marine Animals as Transparent Lantern Slides. 

 By H. C. SoRBY, LL.D., F.R.S. 



For some years past the author has devoted much time to this subject, when 

 on board the yacht Glimpse. The methods which give good results vary much in 

 the case of diii'erent animals. Some must be arranged on the glass and dried 

 quickly soon after having been caught, whereas others ^like Meduste) must be 

 treated over and over agaiu with moderately strong alcohol to dissolve out all the 

 salts. In some cases various staining materials must be used to briug out the 

 structure, and some should be decalcified. 



Usually the animal.« are killed by keeping them for a short time in diluted 

 alcohol, and are then arranged on the glass ; and, after as much of the alcohol as 

 will drain out is lost, they are dried in a current of air. The edges dry first, and 

 so adhere to the glass that, on further drying, the animals become thin without 

 any material change in form. In some cases they must be thoroughly soaked with 

 clear gum before becoming quite dry. Finally, when quite dry, they are mounted 

 in Canada balsam, and the edges of the cover glass very completely bound round 

 so as to prevent the balsam running out when heated in the lantern. 



3. Descri])tion of Methods for Collecting and Estimating the number of 

 Small Aniinals in Sea Water. By H. C. Soeby, LL.D., F.R.S. 



The author described the methods he employs to collect moderately small 

 animals by means of a brown holland bag, at the bottom of which is an arrange- 

 ment so that brass wire sieves with meshes of various sizes can be fixed by a sort 

 of bayonet joint. Through these the water flows readily, and the animals are 

 easily waslied off into a small bulk of water. 



Another method is to collect water in a special bottle at various depths from 

 the surface to bottom, and to pour 2-k gallons through a sieve having openings 

 about ^^-ij of an inch in diameter From this the animals are washed off into a 

 few ounces of water. The numbers of the various kinds are afterwards counted in 

 a small deep narrow trough filled over and over agaiu until the whole quantity 

 has been examined. The number oi each kind per gallon can then be easily 

 calculated. 



