174 



embryo leaves the needle it, in most cases, drops over on its side, 

 but the position of its longitudinal axis remains the same. The position 

 of the embryo on the strip accordingly depends on the direction of 

 the axis of the needle when the embryo is placed. The exact position 

 of the embryo with regard to the rulings can be arranged with the aid 

 of a dissecting or a compound microscope as may be necessary. 



As embryos handled in this way are surrounded by a very small 

 quantity of oil, moving one does not change the position of others on 

 the strip. When the embryos are in position, the strip is submerged 

 in xylol (turpentine and chloroform serve nearly as well) for a minute 

 or two. This removes the oil of cloves, hardens the collodion, and 

 sticks the embryos in position. 



The strip of linen, with the embryos on it, is then imbedded in 

 paraffin. When preparing to section, scratch off the paraffin on the 

 cloth side of the linen, catch hold of an edge, and strip it off. This 

 will leave the embryos imbedded in the paraffin in the position they 

 were placed on the linen. Should they remain sticking to the linen, 

 too much collodion has been used. The lines ruled on the linen ap- 

 pear on the paraffin as ridges that indicate the direction that the ob- 

 jects are to be cut. 



I have found it convenient to arrange small embryos in rows, each 

 one definitely placed, fig. 4, and cut a whole row, sometimes as many 

 as 20 embryos, in a single ribbon. The length of such a ribbon need not 

 be more than the length of a cover glass, if the block is carefully trimmed. 



A broad ribbon is not as likely to curve as a narrow one, and is 

 more easily handled. When cut in this way, a number of series of em- 

 bryos will be side by side where they can easily be compared. 



In conclusion, it may be well to call attention to the two princi- 

 pal causes of failure in the use of this method. Embryos sometimes do 

 not stick to the strip of linen when it is placed in xylol. This is due 

 either to the presence of too much oil of cloves around tho embryos, 

 or to too small a quantity of collodion mixture on the strip. Again, 

 embryos sometimes stick so firmly to the linen that they do not come 

 off in the block of paraffin. This is because too much collodion mix- 

 ture has been used. 



Very few mistakes will be made, as the operator will soon learn 

 how much collodion to use. 



2. Zoological Society of London. 



February 20th, 1900. — Mr. Oldfield Thomas exhibited a specimen of 

 a Kangaroo from Northern Australia allied to Macropus Engenii, but distin- 

 guished by its pale colour and long soft fur. It was proposed to name the 

 species M . Bedfordi, after the Society's President, who had given the specimen 

 to the British Museum. — Mr. Thomas also exhibited a Kangaroo from 

 Western Australia, apparently referable to Macropus robustus, but separable 

 subspecifically by its nearly uniform rufous fawn-colour. It was named Ma- 



