14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



A number of adjacent photographed sections seen at a glance could 

 be evaluated and examined without the distractions accompanying 

 mechanical manipulation of the microscope. The finer details were, 

 of course, checked and filled in from a direct observation of the 

 microscopic preparations under the microscope. A stage micrometer, 

 photographed at the same time and under the same conditions as the 

 sections, afforded a method of accurate measurement, regardless of 

 the enlargement factor. Occasionally tracings were made directly 

 from the photographic enlargements using transillumination. Rapid 

 sketches could be made with little effort and provided handy work 

 sheets of structure outline. The photographic negatives furnished 

 a permanent record of the series, and additional prints could be made 

 when necessary. 



Graphical reconstructions were also made directly from the micro- 

 scopic material. By means of a microprojection apparatus, the dorsal, 

 ventral, and sagittal views of the brain of hipuncticeps were thus 

 constructed (figs, i, 2, 3). With the aid of a stage micrometer, the 

 apparatus was adjusted so that the diameter of the sections corre- 

 sponded to the known thickness (10 micra) of the sections. Each 

 division on the graph paper used (10 divisions to the linear inch) was 

 made equivalent to 10 micra. Equal magnification of each section, the 

 most important condition for accurate reconstruction, was thus in- 

 sured. The reconstruction procedure was as follows : The image of 

 a section was projected onto the graph paper. Pencil dots marked 

 the limits of the anatomical entities which were to be reconstructed. 

 The adjacent section was then brought into position, and dots were 

 made on the next line of the graph paper. Additional sections were 

 plotted until the entity being reconstructed was completely delimited. 

 The dots were then connected by continuous lines, and the resulting 

 outline was shaded for perspective effects in accordance with the ob- 

 served contours in the microscopic sections. The bilateral symmetry 

 of the brain exhibited in the transverse sections facilitated the selec- 

 tion of a reference point in each section. Alignment of reference 

 points on a center guideline drawn on the graph paper insured ac- 

 curate reconstruction. Only one aspect, obviously, can be recon- 

 structed at a time. 



IV. OBSERVATIONS 



GROSS ANATOMY OF THE CEPHALIC NERVOUS SYSTEM 



The cephalic nervous system of hipuncticeps is a small mass di- 

 vided into an anterior supraesophageal and a posterior subesophageal 



