2672 



Journal of Applied Microscopy 



Fig. C. — The egg and the lines of 

 micrometer are drawn with the 

 camera (X70) while the Ulva piece 

 is diagramatically reduced, a h and 

 id represent two (not adjacent) 

 lines of the ruled slide, the distance 

 between these two being also greatly 

 reduced on account of the lack of 

 space. 



along any other line parallel or perpendicular to the axis (a b or c d in Fig. 

 B). When more accurate orientation is necessary, an ocular micrometer, 

 ruled slide, and mechanical stage should be used (Fig. C). The eye 



piece is first rotated until the lines of the 

 micrometer become parallel to those of the 

 ruled slide, the Ulva piece then moved so 

 as to make the axis of the object coincide 

 with a line of the ocular micrometer, and 

 finally cut along any line of the slide, e. g., e f 

 of Fig. C. 



Now let us come back to the subsequent 

 processes. The Ulva on which the object is 

 correctly fastened, is placed in xylol or cedar 

 oil for a few minutes and then imbedded in 

 the usual way. It may be found convenient 

 to imbed the Ulva in a drop of paraffin, and 

 mark the direction of the guide-edge on the 

 drop, or the Ulva piece with the objects on 

 may be preserved in cedar oil, until the time 

 of imbedding. In this way the loss of very 

 sftiall objects is p?-e7>enied, especially in trans- 

 portation. The paraffin block containing 

 the Ulva is trimmed off from the side on 

 which the objects are not attached, leaving a very thin layer of paraffin 

 over the guide-edge. The block is then set on the carrier of the micro- 

 tome so as to make the guide-edge parallel to the knife and the Ulva piece 

 vertical, with the aid of a hand-lens. This is of great importance ; for, if this 

 be neglected, the orientation of the object will be lost. After the block is rightly 

 set the guide-edge is trimmed until the object appears just beneath the surface. 

 The sections are cut without paying attention to the object itself, and when 

 mounted the objects will be found cut exactly through the desired axis. 



The Ulva method, as we have seen, is very simple, and a few trials will con- 

 vince one of its accuracy. Moreover, it seems to have a few advantages over 

 Patten's method : (1) the transparency of the Ulva helps orientation of small 

 objects under a fairly high power, (2) in using Ulva it is not necessary to pull 

 the substratum off from the paraffin block, and consequently any amount of 

 celloidin-clove-oil can be used according to the nature of the object, and (3) not 

 only does the Ulva not interfere with the sectioning, but the sections of Ulva 

 serve as guide-lines in reconstruction. 



In conclusion, I may mention another important use of celloidin-clove-oil 

 described by Patten. In mounting small objects, it often happens that they slide 

 out toward the margin of the cover-glass, or, if not, they will not stay in the 

 desired position. In these cases, celloidin-clove-oil followed by xylol keeps 

 them in any desired place and position. Celloidin-clove-oil is, therefore, often 

 indispensable in mounting in regular order many small objects under one cover- 

 glass, e. g., developmental stages of annelids and echinoderms, appendages of 

 small crustaceans. N. Yatsu. 



Zoological Laboratory, Columbia University. 



