Marcu 22, 1912] 
The celluloid is cut with the shears to the required 
size and shape and the boxes are built by cement- 
ing the edges of the sheets by bringing them into 
the desired position and then moistening them with 
acetone applied with a small brush. Less than a 
minute is required for the firm adhesion of the 
edges. In the same way the celluloid can be 
fastened to the edges of a light of glass, provided 
that the edges of the latter be clean. Of course 
considerable care must be exercised to see that all 
pieces of celluloid be accurate in size. The details 
of the operations are not easily described, but a 
little experience will enable any one to devise 
methods to meet all cases. The specimen can be 
fastened to the glass or celluloid by means of 
scraps of the waste celluloid dissolved in acetone. 
I have now fluid specimens mounted in ‘‘ Wilson’s 
oil’? and enclosed in boxes of celluloid, built up 
in the same manner, which have been in good con- 
dition for several months. How permanent they 
will prove, time can only decide. It is impossible 
to mount them in alcohol or formol as water or 
alcohol dissolve the camphor and other substances 
in the celluloid. In the case of Wilson’s oil the 
box must be completely filled or there will be a 
warping of the celluloid which will break down the 
box in a few days. I believe that celluloid can be 
used to fasten the tops to the square museum jars, 
but I have not tried it. I may suggest that strips 
of celluloid be fastened to the ground edge of the 
jar by acetone, the jar be then filled as completely 
as possible with the preserving fluid without wet- 
ting the edge of the celluloid, and then the cover 
applied, acetone being run in with a brush, and 
then a solution of celluloid in acetone being painted 
over the joint. It seems probable that, with such 
a thin layer of celluloid, there would not be suffi- 
cient warping to break the joint. It is often de- 
sirable to mount rather thick microscopic objects 
under pressure. I have used the following process 
in thus mounting parapodia of annelids. Two 
narrow strips of sheet celluloid are placed on a 
slide in the desired position and are then cemented 
to the slide by running acetone under them. The 
object, properly cleared, is placed between the 
strips, and the cover-glass pressed down and 
fastened in position with acetone run under. In 
two or three minutes balsam or dammar is drawn 
under the cover by capillary attraction and the 
slide is permanently mounted. I may say that the 
sheet celluloid is to be had in every large city. 
I have bought my supplies of Willard and Willard, 
65 Bedford Street, Boston. The scraps from other 
SCIENCE 
467 
operations may be used, instead of gun-cotton or 
celloidin, for section cutting, being dissolved in 
alcohol and ether in the customary manner. 
Parasites of the Muskrat: F. D. BARKER, Univer- 
sity of Nebraska. 
On the Number of Known Species of Animals: 
H. 8. Pratt, Haverford College. 
The first enumeration of all the species of ani- 
mals known to science was made by Linneus in 
1758. In the tenth edition of the ‘‘Systema 
Nature’? he described 4,236 species, which were 
apportioned among the various larger groups 
(which are here given their modern names) as 
follows: 
Mam mall sur inary sre alelsveyentelensuep iene ratapcres 183 
ISTE Ve HOO CHEE oe OCIS aI oraers 444 
Birds and Amphibians ............... 181 
HOES Scio b oo HOBBIES Ge HaEpO coos citad 414 
Muni catesysaerercieionelteiohere co robatons eleiekerey estore 3 
ISIMTOADE) Kooodocovcsonoceoauosdodcdon 35 
Mollusks and Brachiopods ............ 674 
Crustaceans seine err ee 89 
HAT ACHNTAS Me yetsteusiaeiclerensleyetsivaleucenetoheretele 78 
WypMEyDOGR Gooossoqccnoadogcooddnoas0 16 
IGNEHOHS doodocdodaocob0ns oon0gDDNe S000 1,936 
WOME ‘saisoooondddabcdsdcosgogcboos 41 
HH Chin‘gdermswacaericereeec kere ieieiien rere 29 
Cwlenteratal serum eves Woche ust 74 
SOMES seaccocncbocoenendoo0onop00 11 
IDOE) be acdonoonnoeod copaaOoOnadoo 28 
About a hundred years later (1859) Agassiz and 
Bronn made the following enumeration: 
WOMANI, oocooscbcandccuc000000n 18,660 
OMI oooocedoscocneadaaon0N000 11,600 
CHERTAGERME cos oadcooesonvooscusye 1,500 
ATCC G55 5encocpbsoacacnbendce 2,000 
IMME LodiscodareoagoccovoucodsacK00 90,000 
WGN coggagbupopedcaooooMoooGO00 1,600 
Hichinodenmnsieaee erties 550 
Coslenteratesierrasiieertritrlerieiteretls 1,820 
SIONS. Goooodosgodsoccagde0e50000 290 
IPKOUWOAE, Saodadooasaeaqoodsoboddodd 1,510 
129,530 
In Ludwig’s revision of ‘‘Leunis,’’ published in 
1886, the numbers of species are given as follows: 
WEMMBI Gobsdadcasdocoooogood soo 2,300 
Bird sper veer alew sil avetalcee sai) evetebs 10,000 
INOUE) Gas odoauecccscpoocKGouODNUd 2,500 
ANIM WHEN oo soc0udc0ccl00000000000 1,000 
IMG oa ocaggossyapannoD ooo KGOODN 9,000 
UN WHUCRNIE! socboocacanoucounoqooHe 300 
MIDE 55 000c6nen06b00d08000000 21,320 
