A^t) LIFE-HISTORY OF DIATOMS. 423 



These inclusions, formerly i-egarded as fatty in nature, are the 

 so-called red granules (roten Kornchen) of Biitschli, and merit 

 a somewhat detailed consideration. 



We owe to Biitschli the differentiation of these spherules from 

 oil globules, and the recognition of the property they possess of 

 taking an intense red-violet stain with Delafield's haematoxylin, 

 as also of staining, intra vitam, with methylene blue. He noted 

 their wide distribution in Bacteria, Cyanophyceae, Filamentous 

 Algae, and Flagellata, as well as in certain Diatoms, and at one 

 time considered them to be nearly related to the chromatin 

 granules of the nucleus, but Lauterborn's researches did not lend 

 support to this view. 



A noticeable feature in connection with these Biitschli's 

 spherules is their very characteristic distribution in certain 

 Diatoms, often affording, indeed, good specific characters. Lauter- 

 born's descriptions are too detailed for reproduction here, but 

 one or two of the most interesting examples may be briefly 

 mentioned. 



Thus, in Navicida cuspidata, there are two of these spherules, 

 usually measuring from 6 — 9/x in diameter, and placed one on 

 either side of the median protoplasmic bridge containing the 

 nucleus (Fig. 5, h.s). Pinnularia ohlonga agrees in the number 

 and positions of the spherules, but each of them is surrounded 

 by a conspicuous vacuole bearing on the side turned towards the 

 extremity of the cell a crescentic, cup-like body of a grey colour, 

 which, unlike the spherules, stains neither with haematoxylin 

 nor with methylene blue (Fig. 1, t). These appendages vary 

 in size, and are frequently vacuolated. They are absent in 

 Cymhella cuspidata, which possesses two spherules (each sur- 

 rounded by a vacuole) placed at the extremities of the cell 

 (Fig. 3, b.s). 



In Surirella calcarata and S. splendida Lauterborn notes the 

 presence of numerous small granular bodies exhibiting active 

 movements. They appear to be generally distributed over the 

 surface of the protoplasm, and may be watched gliding here and 

 there, now coming to rest for a short time, then suddenly starting 

 into activity again. The general direction of movement would 



