140 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
frequently at first. If it is wished to preserve some of the larger 
Selachians for some months in order to prepare at leisure the skeleton, 
the intestines should be removed, and the animals placed in a 10 per 
cent, solution of salt. 
Elasmobranch embryos may he fixed in corrosive sublimate, leaving 
them in the solution for 5 to 15 minutes, afterwards washing well in 
iodized alcohol. Embryos of Torpedo with the yolk were preserved by 
immersing them in a mixture of equal parts of 1 per cent, chromic acid 
and corrosive sublimate for 15 minutes, and then transferring to alcohol. 
Transparent fish-eggs may be preserved for the purpose of demonstration 
by subjecting them for a few minutes to the action of the alcohol and 
hydrochloric acid mixture, and then transferring them to pure alcohol. 
Some Hints on the Preparation of Delicate Organisms for the 
Microscope.* — Mr. E. Lovett observes that such organisms as the ova of 
Mollusca, Crustacea, fishes, &e., are often of such a nature as to be very 
difficult of permanent preservation, but he has succeeded in overcoming 
the difficulty satisfactorily by means of a fluid, the density of which he 
modifies in accordance with the organism about to be mounted. The 
fluid was composed as follows : — Three parts pure alcohol, two parts 
pure glycerin, and one part distilled water. This strength was suitable 
for young crustaceans, the ova of the fishes, and for the tougher ova-sacs 
of the Mollusca. For the ova of crustaceans and insects, and for those 
of very small fishes, one or two parts more of distilled water may be 
added ; whilst for such exceedingly delicate substances as the ova of the 
nudibranchiate Mollusca, zoophytes extended from their capsules, and 
for various delicate fresh-water forms, a weaker formula than this is 
necessary ; but as practice is the best instructor, he recommends students 
to be guided by what they find to be the best proportions. 
This fluid should be put into small glass tubes, with corks bearing 
numbers corresponding to those in a note-book, so that full details of 
the contents may be recorded. These tubes should be taken down to 
the shore by the collector, and the organisms should be placed therein 
alive, direct from the sea. The length of time required for the pre- 
servation of the object by the fluid varies, according to the organism, 
from a week to a year, but some of Mr. Lovett’s best preparations had 
been soaking, before being mounted, for five or seven years ; and as a 
proof of the value of the preservative fluid, he cites the mucus-like 
ova mass of an Eolis, which was in quite its natural condition, although 
eight years of age as a micro-slide. The cement used by Mr. Lovett 
for fixing cells for this fluid, for fixing the cover-glasses to the cell-wall, 
or for covering sunk cells, is composed of equal parts of red lead, white 
lead, and brown litharge, pounded to a powder and kept dry. When 
wanted for use, a little is mixed with japanner’s gold size as thick as 
required, and it must be used with great care to insure success ; but in 
this case also practice is the best way to satisfactory results. 
Improved Method of preparing Ascidian Ova-t — Dr. T. H. Morgan 
found that the ordinary methods of preparation do not show the boun- 
daries of the cells of the follicle in sections of young ova. He made, 
* Trane. Croydon Micr. and Nat. Hist. Club, 1889-90, pp. 203 -4. 
t Journal of Morphology, iv. (1890) p. 198. 
