1895 THE MICROSCOPE. 73 



Finally, in section D, there are from four to seven or 

 more joints in the shell, (see Fig. 32). The first joint is 

 still known as the cephalis, the second as the thorax, the 

 others as abdominal joints, first, second, third, etc., the 

 first abdominal joint being the one next the thorax. By 

 a vertical basal spine is meant a spine on the last of the 

 abdominal joints (which in such forms is closed), point- 

 ing in the opposite direction from that which a horn on 

 the cephalis would take. 



In conclusion let me say that the student should make 

 some type slides for himself, if he wishes to get an idea 

 of the classification. There are too many forms on a 

 strewn slide for comfort. A type slide of 20 or 40 dif- 

 ferent forms will be the most convenient for study. The 

 mechanical finger furnished by Bausch and Lomb is very 

 handy for this purpose, but in place of the hair which is 

 supplied with it I use a fine glass hair made from a 

 small glass rod which has been heated in the middle over 

 an alcohol lamp or a Bunsen burner. Just as it begins 

 to melt, the two ends are drawn apart rapidly as far as 

 the arms can reach, and the result is a long, fine thread 

 which floats in the air. Let it settle on the table and 

 cut off" a bit of the thinest portion about half an inch 

 in length. Then make a wedge of beeswax, rounded on 

 one side, flat on the other, and press the hair on the flat 

 side so that it projects beyond the wedge point about an 

 eighth of an inch. Press the wedge on the steel rod of 

 the mechanical finger and adjust the finger on the micro- 

 scope and you are ready for work. In place of a glass 

 hair, I have used a hair of sealing wax with much better 

 results as the forms do not spring ofl" from it as they do 

 from glass. 



The student will do well also to procure a copy of 

 Ehrenberg's work, the title of which is "Fortsetzung der 

 mikrogeologischen Studien, etc." Yon Christian Gott- 



