AND LIFE-HISTORY OF DIATOMS. 



419 



oblonga (Fig. !,/>.)• They exhibit a fine and even reticulation 

 with a clearly-defined alveolar border where the protoplasm is in 

 contact with the valves and skirts the cavity of the vacuole. 



In Surirella, at the commencement of nuclear division, 

 Lauterborn noted the presence of closely-crowded delicate 

 fibrillae radiating from the centrosome and prolonged through 

 the various protoplasmic processes into the most remote 



Vac 



MU. 



1. 



2. 



3. 



Fig. 1. Pbmularia ohlonga (resting stage). Lateral view showing 

 Biitschli's spherules h.s., chroraatophore ch, nucleus mi, terminal 

 masses of protoplasm p, cap-like bodies t, and vacuoles vac. (After 

 Lauterborn.) 



Fig. 2. Pinnidaria major. Lateral view showing centrosome c, chro- 

 matophore ch, paired rods, " doppelstabchen " dst, protoplasmic fibrils 

 /, nucleus nu, nucleolus nl, and oil drops ol. (After Lauterborn.) 



Fig. 3. Cywhella cusjndata. Surface view. Lettering as in Fig. 1 and 

 ^y = pyrenoid. (After Lauterborn.) 



regions of the cell (Fig. 6), but these he regarded as being 

 in reality the walls of radiating cellular compartments, and 

 not simple thread-like structures as might at first be imagined. 

 A similar structure was also noticed in certain parts of the 

 protoplasm in resting examples of Surirella calcarata. The 



