ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 157 



processes and cells or enable one to trace the cell process so well as 

 the method of soaking in the picrocarmine before cutting ; there is 

 also little risk of damaging the sections after they are cut, as they 

 can be washed off from the razor to the slide, cleared with oil of cloves 

 and mounted in dammar varnish or balsam dissolved in benzole in the 

 usual way. 



It is very difficult to procure good picrocarmine in this country. 

 The best thing that I have met with I obtained ready made from 

 MM, Eousseau and Son, Paris. The only objection to the bichro- 

 mate-of-ammonia method is that the solution is liable to deposit in 

 the form of small specks amongst the nerve. Some of these specks 

 are seen in the sections." 



Preparing Teleostei for showing Development of Thyroid and 

 Thymus Glands.* — Dr. F. Maurer studied the development of these 

 glands chiefly in the trout. From eggs obtained recently spawned, 

 the troutlets emerged in forty-eight to fifty-six days. Chrom-acetic 

 acid was found to be the only satisfactory hardening agent (1/2 per cent, 

 chromic acid, 1 per cent, acetic acid, in distilled water). During the 

 first twenty days no deformity of the embryo need be anticipated, 

 but from this period the amount of distortion goes on increasing. 

 The eggs remained in the chrom-acetic from eight to twelve hours, 

 they were next washed in water, and then, after the removal of the 

 yolk, transferred to alcohol. Staining was always performed with 

 alcoholic borax-carmine. In order to prepare the specimens for 

 imbedding in paraffin, they were soaked in absolute alcohol, and 

 afterwards in chloroform. Giessbrecht's shellac method was adopted 

 for mounting in series. 



For examination of the mature thyroid and thymus, these glands 

 were injected with a watery solution of Berlin blue thickened with 

 gelatine. The injection was effected by snipping off the apex of the 

 heart and passing the canula through the ventricle into the bulbus 

 arteriosus. 



Permanent Mounting of Tracheae of Insects.f — Mr. F. T. Hazle- 

 wood has succeeded in a very simple way in mounting permanently 

 the tracheal system of insects. 



He dissects out the soft parts and spreads them on a glass slide of 

 the usual size ; lets them dry perfectly ; and then with pencil- brush 

 gives them a good coating of collodion. After this melt a little hard, 

 pure balsam in a test tube, and put it on the object with a cover-glass 

 applied at once. 



This method is remarkable for its results. The intestines, the 

 ganglia, and the brain, are " perfectly magnificent." The intestine 

 makes thus one of the most beautiful objects for dark-ground illu- 

 mination. The brain shows the most abundant ramifications of the 

 trachea, especially in the immense parallel branches in the rods of 

 the eyes. The ganglia can be floated on a cover-glass, dried, and 

 mounted in this way. 



* Morphol. Jahrbuch, xi. (1885) pp. 136-8. 

 t The Microscope, v. (1885j p. 235, 



