Smallwood, MoUuscan Nerve Cells. 



187 



Fig. 4. 



spaces there is a considerable amount of densely staining sub- 

 tance similar to that described in Fig. 2. 



Figure 4 again shows the Nissl bodies rather numer- 

 ous and completely filling one end of the cell. The 

 nucleus is evidently undergoing division as indicated by 

 the state of the chromatin lying free in the cytoplasm. 

 There are a few lymph spaces near one edge of the cell, 

 close to the cell membrane. 



Planorbis. — The fresh nerve collar of Planorbis was placed in a 

 3 per cent, solution of osmic acid for eight days. In hundreds of 

 cells obtained by this method, the conditions were much as shown 

 in Fig. 5. Here there seems to be a 

 nearly typical distribution of Nissl 

 bodies. The appearance of these / o^ 

 bodies is more like the usual condi- 

 tions for the Nissl flakes. When {^'■ 

 other stains are used a fine granular 

 cytoplasm is then evident. There 

 are scattered in the cytoplasm a Fig. 5. 



number of lymph spaces with no apparent regularity of form or 

 position. Most of the nucleoli contained a central vacuole. Apart 

 from the lymph spaces represented in the drawing this nerve 

 cell would be typical of many of the nerve cells reported by 

 Rhode. 



Limax. — Collections of Limax were made October 13, 1903, 

 from a brick walk on our campus. A part of the specimens were 

 killed at once in several of the best fi.xing reagents and the remain- 

 der were placed in a dark, moist chamber having plenty of grass. 

 The conditions in Fig. 6 are such as are common in the freshly 

 collected animals, while in Fig. 

 7, the nerve cells exhibit many 

 unusual structures after being 

 kept in the dark for seventy- 

 two hours with plenty of grass. 



In Fig. 6 the lymph spaces 

 are very large and distributed 

 irregularly. The cytoplasm 

 seems to be free from Nissl Fig. 6. 



bodies or other densely-staining granules. In the nucleus there 

 are two large nucleoli. The chromatin is evenly and loosely 



