ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
883 
and of illustrations. For a first edition the illustrations are unusually 
numerous, for there are 221 of these, partly wood-engravings and partly 
zincographs, some being coloured. There are, as well, eight lithographic 
and photographic plates. 
Preservation of Teleostean Ova.* — Mr. Walter E. Collinge states 
that between October 1891 and July 1892, upwards of 80,000 ova have 
been examined at the St. Andrews Marine Zoological Laboratory, 
comprising some thirty known and four or five unknown species. He 
has made numerous experiments with various preservatives on a large 
number of these, and gives an account of the results obtained. 
Killing. — The most satisfactory results were obtained by adding to 
a vessel containing the ova, with about an ounce of sea-water, three 
or four drops of a saturated solution of picric acid, to which had been 
added 5 per cent, of hydrochloric acid. In this diluted solution they 
were allowed to remain for not longer than three minutes, during 
which time they were kept in motion by a pipette. When the ova 
remained for longer than the time stated, or when the solution was 
too strong, the yolk was generally ruptured, and considerable wrinkling 
took place in the zona radiata. In other cases the yolk became con- 
siderably contracted. Like results ensued if they were not well washed 
in fresh water before being transferred to the preservative fluid. After 
washing in dilute alcohol 12J-25 per cent., a slight opacity followed. 
If killed in a saturated solution of 6 parts corrosive sublimate and 
3 parts of glacial acetic acid they were also opaque when transferred to 
any of the following fluids. 
Preservatives. — Some dozen or so of picric mixtures were tried, of 
which the following are the principal : — 
(1) In equal parts of a saturated solution of piero-hydrochloric acid 
and 50 per cent, alcohol, ova of Trigla gurnardus shrank • 1524 mm. ; 
the yolk was contracted and opaque ; the oil-globule scarcely visible. 
In Pleuronectes platessa the shrinkage was slightly less, I being 
*1447 mm. 
(2) Saturated solution of picric acid, 1 part; glycerin, 1 part; 60 
per cent, alcohol, 2 parts. Motella mustella shrank • 1524 mm. ; the 
oil-globule was fairly distinct. 
(3) Saturated solution of picric acid, 2 parts ; alcohol, 1 part. 
Results very similar to method 1. Shrinkage fully *1524 mm.; oil- 
globule poor and embryo indistinct. 
(4) Saturated solution picric acid, 2 parts ; 50 per cent, alcohol, 
4 parts ; 2 per cent, acetic acid, 1 part. Motella mustella and Trigla 
gurnardus; oil-globule and embryo indistinct; zona strongly wrinkled. 
(5) Equal parts of saturated solution picric acid, alcohol, and two 
per cent, acetic acid. The following ova were preserved in this fluid, of 
which the average shrinkage is given. The oil- globule, where present, 
was remarkably clear. Embryos very distinct. Ova previously 
prepared in other fluids, in which the oil-globule was scarcely or not at 
all visible, speedily came to view when allowed to remain in this fluid 
for five to twenty minutes. 
* Ann. and Mag. Nat. Hist., x. (1892) pp. 228-30. 
f The average in all cases is given. 
