300 First Maturation Spindle of Ailolobophora Footida 



Method. 



In the summer of 1901, Ave fixed and sectioned a larp-c nnml)er of 

 reccptacula ovonnn. but we found this a very unprofitable method; 

 accurate study of the normal egg being very much hampered by the 

 number of abnormal eggs found in the receptacula, in some cases the 

 entire receptaculum being filled with eggs in various stages of degenera- 

 tion. We found in one receptaculum ovorum as many as forty eggs and 

 of these only four were normal. A more- serious diflficulty was the un- 

 favorable action of the fixative on the receptaculum as a whole. The 

 swelling or shrinking, or the combination of both, produced by some fixa- 

 tives, acts with intensified effect on the mass of eggs crowded into the 

 receptacula, often distorting the normal eggs in a way to render them 

 valueless for cytological study. 



In the summer of 1902, Ave tried removing the eggs from the receptac- 

 ula after they had been cut from the worm and placed in a watch glass 

 in distilled AA^ater. By carefully teasing the walls of a receptaculum, 

 under a dissecting microscope, the eggs can be pressed out, and only those 

 that appear normal selected for stud}', the subsequent technique being 

 the same used for eggs collected from the cocoons (Foot, '98). The fol- 

 loAving fixatives Avere used, chromo-acetic, corrosive sublimate, corrosive 

 acetic, Eabl's picro-sublimate, Boveri's picro-acetic, picro-sublimate, Flem- 

 ming's chromo-aceto-osmic, and the same proportion of chromic and osmic 

 omitting acetic acid. Hermann's platino-aceto-osmic and the same pro- 

 portion of osmic and platinum chloride, omitting the acetic acid. A 

 comparison of the photographs AA'ill shoAv that the platino-osmic has 

 proved the least injurious to both nuclear and cytoplasmic structures. 

 The sections Avere stained Avith iron-hffimatoxylin foUoAved by dilute 

 Bismarck broAvn, or Avith Bismarck broAvn alone. In some cases, un- 

 stained sections give the most satisfactory photographs. This is especially 

 true for archoplasm, AA'here in stained preparations the dense stain 

 taken by the archoplasm produces such a strong contrast to the faintly 

 stained cytoplasm, that it is impossible to get an accurate reproduction 

 of one Avithout sacrificing the other. All the preparations AA^ere stained 

 with the end in vicAv of securing satisfactory photographs, as aa'c aim to 

 present only such cytological phenomena as can be clearly demonstrated 

 by photography. 



The impossibility of securing a clear demonstration of the prophases 

 in fixed and sectioned eggs led us to devise a ncAv method AA'hich is a 

 modification of the smear method. Instead of smearing a mass of eggs 

 on the slide, Ave handle each egg separately. After isolating a liA'ing egg 



