734 SUMMARY OF CURRENT RESEARCHES RELATING TO 



crystals of thymol. The osmic acid is especially reduced at the 

 bifurcations of the blind ending tracheal capillaries within the 

 luminous plates, and in the tracheal branches before the bifurcation. 



Another method of preservation consists in injecting corrosive 

 sublimate solution into the animal, and subsequent treatment with 

 alcohol. 



Preparing Embryo of Peripatus Edwardsii and P. torquatus,* 



— To obtain the embryos uninjured, Prof. J. v. Kennel removes 

 them with the uterus from the chloroformed mother-animal, and 

 places them, partly in concentrated solution of corrosive sublimate, 

 partly in 1 per cent, osmic acid solution, and subsequently hardens 

 them in alcohol. Alcohol alone, chromic, picric, or picro-sulphuric 

 acid cannot be used for hardening, as they alter the object. The uterus 

 is rendered transparent by turpentine, and cut with its contents, or 

 the embryo is taken out and cut alone. 



Preparing Diatoms from the Stomachs of Mollusca and Crus- 

 tacea.f — Mr. E. S. Courroux recommends that in the case of mussels 

 and cockles, the stomach should be cut out and steeped, or even 

 boiled, in nitric acid until it is dissolved, and the resultant deposit 

 washed and cleaned after one of the methods recommended in the 

 text-books. A little special care, however, in the treatment of 

 shrimps' stomachs will not be thrown away. On removing the shelly 

 skin at the back of the head, the stomach will be seen as a small, 

 dark-coloured body, the size of a small pea. Its position may gene- 

 rally be detected in the perfect shrimp from the dark appearance at 

 the back of the head. The stomachs may be detached with the 

 point of a knife, and when some 12 or 20 or more (as the deposit 

 obtained from them is small) have been collected, they should (taking 

 care that the skin of each stomach is cut or broken) be boiled for a 

 few seconds in a weak solution of washing-soda or ammonia, and 

 then immediately be thrown into a beaker of cold water. By these 

 means we get rid of grease, &c., and render the subsequent treatment 

 by acids more easy. The empty skins of the stomachs will float, 

 and may be picked out of the solution. 



The residue which collects after the solution has stood for some 

 time should first be washed free from alkali, and then treated with 

 acids in the usual manner. 



The method of separating deposits into different densities is very 

 useful here as with many other gatherings of diatoms, inasmuch as 

 the large forms are then more easily isolated. The often advised 

 whirling in a large evaporating dish in order to separate the diatoms 

 from sand and debris may be frequently practised with success. In 

 the washings of all diatoms, the author has found it of the utmost 

 advantage to perform the later rinsings in distilled water. The 

 diatoms are thus more effectually cleaned from salt, &c., and present 

 less attraction to moisture in the case of dry mounts. 



* Arbeit. Zool.-Zoot. Inst. Wiirzburg, vii. (1884) pp. 1-222. 

 t Joiirn. of Microscopy, iv. (1885) pp. 19tJ-8. 



