. Journal of applied microscopy and laboratory methods. edto a distance. By means of the adjustment screws, the arc is then brought intosuch a position that the glowing crater occupies the center of the field. Prelim- 1160 Journal of Applied Microscopy inary to this, however, the substage condenser has been racked up with thecoarse adjustment until it brings the image of the crater into focus at the levelof the object. If the camera has not been adjusted with reference to the opticalbench, it is now arranged so that the image of the crater falls in the center ofthe ground glass. Provided the s
. Journal of applied microscopy and laboratory methods. edto a distance. By means of the adjustment screws, the arc is then brought intosuch a position that the glowing crater occupies the center of the field. Prelim- 1160 Journal of Applied Microscopy inary to this, however, the substage condenser has been racked up with thecoarse adjustment until it brings the image of the crater into focus at the levelof the object. If the camera has not been adjusted with reference to the opticalbench, it is now arranged so that the image of the crater falls in the center ofthe ground glass. Provided the substage condenser is properly centered, thelinear adjustment of the combination is complete. The next step is to arrange the object with reference to the condenser andthe objective which is to be used in making the negative. I have found itadvantageous to connect these three elements with homogeneous immersionfluid and for a condenser employ the parachromatic oil immersion form madeby Watson & Sons. The objective is an apochromatic I mm. of Figure 2.—Transformation stages between tlie telophase of the spermatogonia and the ]irophase of the first spermatocytes. The gradual accimuilation of the chromatin into a thread may he noted. Successive stages shown at a , b , and c . Same object. 1000 diameters. For a number of reasons, it is convenient to interpose temporarily anincandescent gas lamp in the substage series while getting the proper focus andadjustment of the object with the eye. When this adjustment has been accom-plished, it remains only to get the final projection of the image upon the groundglass of the camera before the exposure is made. The projection eyepiece is now substituted for the observation ocular, whichhas been used up to this time, and an image thrown upon the small screen whichstill hangs upon the front of the camera. Here an approximate focus of bothobject and source of illumination is obtained and the composition of the picturestudied. If this i
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