CYTOLOGY OF THE MYXOMYCETES. 83 



cavity contains only materials in solution in the cell-sap. These 

 materials may be used up in the formation of the capillitial wall 

 and spirals so that in late stages no such precipitation products 

 are formed." 



In the first place my observations show, contrary to Harper and 

 Dodge, that the granular material is quite abundant in well 

 formed capillitial threads. In Fig. 17 of Arcyria denudata the 

 granules are very numerous and occupy almost the whole interior 

 of the thread. In fact I have never found them to be so abundant 

 in early stages in the formation of the capillitial threads in Hemi- 

 irichia clavata. Neither have I found any indication that granu- 

 lar material as such passes from the interior of the thread into 

 the forming spirals (see Figs. 13, 15, 17, 18 and 19). It is hard 

 for me to believe that these granules are precipitation products 

 formed by fixation. It will be noted that they are often of 

 astonishingly uniform size and shape which one would not expect 

 in products of precipitation or coagulation. Moreover they are 

 often absent or isolated or distributed evenly over the interior of 

 the thread showing little tendency to clump, which one would 

 likewise expect in the case of products of fixation. They do re- 

 semble mitochondria very closely. Their rod-like and even 

 filamentous shape is well illustrated in my figures. They are 

 often arranged in rows, suggestive also of mitochondria. They 

 are usually about the same size as mitochondria but they are 

 sometimes larger, as shown especially in Fig. 17. Their staining 

 reactions also are suggestive of mitochondria, for they take the 

 fuchsin as well as the iron hematoxylin, after fixation in Regaud's 

 fluid. Nevertheless we cannot consider them to be mitochondria 

 because they occur within the capillitial tubes, quite apart from 

 nuclei and from protoplasm. It would appear more probable 

 that they constitute merely a part of the material brought in, 

 which is useless in the formation of the capillitial wall. 



Harper and Dodge refer to two types of nuclei at this stage in 

 Hemitrichia clavata and I have been able to confirm their finding 

 as illustrated in Fig. 19. It will be seen that the majority of the 

 nuclei are large and pale and have definite nucleoli. Some, 

 however, are smaller and much more intensely stained with the 

 hematoxylin: these Harper and Dodge regard as undergoing 



