ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
805 
mussels are imperfect, either because they are too slow, or they allow 
the blood to mix with water. He advises that the mussel should be well 
cleaned and dried, and without being opened its heart shonld be pierced 
with a needle. Some blood is then collected and examined at once under 
the Microscope, because after one minute obvious pathological changes 
take place in the corpuscle. 
Control preparations are made of blood preserved with osmic acid or 
palladium chloride (1 per cent.) and obtained either by the direct action 
of the reagents, or by injecting the animal in the organ of Bojanus with 
1/2 to 1 ccm., using a Pravaz syringe. Other reagents mentioned do not 
appear to have given satisfactory results. 
When examining the blood of Arthropoda, rapidity is still more 
urgent, since degeneration begins to set in in 10 seconds. From 
Palsemon blood is best obtained by perforating the posterior third of the 
body, in spiders by an incision in the thorax, from Libellulidse larvae by 
cutting off the head, and from insects by tearing off a wing. One device 
mentioned is to drop the blood or dab the organ exuding blood in a small 
drop of the fixative fluid previously placed ready on the cover-glass. 
Blood of Arthropoda should be treated in a manner similar to that 
used for Mollusca, i. e. with one per cent, osmic acid or palladium 
chloride. If 3 per cent, acetic acid be used at once, it will fix the 
amoeboid forms, but if the addition be delayed until the first or second 
stage of degeneration, these appearances are lost. 
Preparation of Sections of Ammocoetes.* — Dr. W. H. Gaskell 
mainly relied on serial sections, the whole head having been imbedded 
in paraffin, or the brain was dissected out and then imbedded. 1 per cent, 
osmic acid, Perenyi’s fluid with alcohol afterwards, with subsequent 
staining in boro-picro-carminate or picro-carmine and eosin were used ; 
for staining on the slide anilin colours and hsematoxylin were used. 
The sections were mounted in order ; when they were so large that they 
were apt to be crumpled, the folding was got over by simply floating 
the series of sections on the surface of warm water and then transferring 
them to a slide previously coated over with albumen and glycerin. 
Arrangement of Pigment in Eye of Arthropods.! — Mdlle. M. 
Stefanowska, in studying the arrangement of pigment in the eyes of 
Arthropods exposed to varying quantities of light, decapitated the 
animals, and at once divided the head longitudinally. The pieces were 
placed in a 1 per cent, solution of osmic acid. The time required to fix 
the histological elements varies, and can only be determined by trial ; 
on the whole, however, the time varies between one and four hours. The 
eyes were next placed in a 25 per cent, solution of oxalic acid with 
alcohol; they were then washed in 70 per cent, alcohol and put into 
absolute. 
After inclusion in paraffin, sections were made with Schauze’s 
microtome ; these demanded much time and patience, as the sections 
break easily. The richness in pigment forms one of the great difficulties 
in preparing sections, which must, therefore, be very fine; those made 
were generally 1/100 mm. in thickness, and it was only with some of 
* Quart. Journ. Micr. Sci., xxxi. (1890) p. 382. 
f Rec. Zool. Suisse, v. (1890) pp. 155-9. 
