638 C. CLIFFORD DOBELL. 



as follows, and may be easily seen in the living animal : — 

 The chromatin which was at first evenly distributed through 

 the nucleus becomes massed in granules at the periphery, 

 whilst the nucleus itself increases in size until it becomes 

 sometimes double its original diameter (text-fig. 2, a, h). 



■«l .fit 



«-. 6 . c . fZ e . 



Text-figuke 2 (from permanent preparations, stained wilh Heidenhain's 

 iron-lijEmatoxylin). 



The chromatin becomes evenly disposed in a single layer, 

 so that in optical section the nucleus has a very character- 

 istic annular appearance (c), the ring being thickened at 

 various points (see also Plate, figs. 8, 12). A typical atri- 

 chous form is therefore distinguished by having no cilia, by 

 possessing " eosinophile globules " and a large ring-like 

 nucleus (or nuclei). When first seen they have a remarkable 

 appearance, and their connection with the ordinary Opalina 

 would hardly be suspected. These forms are quite motion- 

 less. 



In many of the larger atrichous forms division of the 

 nucleus takes place, followed frequently by division of the 

 cytoplasm. Division may be equal, by a constriction appear- 

 ing in the middle (text-fig. 2, d), or unequal. In this latter 

 process a blister-like elevation of the chromatin appears, and 

 is finally constricted off. This is shown in text-fig. 2, c. 

 Above is a cap-like outgrowth of the chromatiu, whilst below 

 a later stage is seen in optical section (cf. also Plate, figs. 10, 



When cytoplasmic division follows the result is either 

 equal bipartition or budding (cf. Plate, figs. 9, 10). The 

 buds so produced are sometimes very small, not reaching a 

 greater diameter than 4 — 5^. Occasionally buds are pro- 

 duced in which no nuclear material whatsoever can be 



