LIFE CYCLE OF GYMXODIXIOIDES INKYSTANS 11 



may remain undigested for weeks or even months, thus pro- 

 viding a unicjue example of the persistence of a protein in a 

 foreign protoplasm. 



What is the intimate structure of these ciliates? The 

 troi)hic phase, as it may be seen after silver impregnation, 

 shows nine rows of cilia diverging from the anterior pole or 

 its vicinity. Each of these rows has a given pattern, con- 

 stant for the species. Four short rows are present in the 

 equatorial sector of the ciliate. The rosette or mouth organ, 

 not represented on the scheme, is located at the anterior end 

 of the rows x, y, z. Each of the ciliary rows or kinety 

 has a line of kinetosomes. At their right, the right of the 

 ciliate (which corresponds to the left of the observer), is 

 a fine thread w^hich underlines the line of kinetosomes. In 

 all ciliates, this kinetodesma is always at the right of the 

 kinetosomes. This is the law of desmodexy [E. Chatton, 

 A. Lwoff (1935b)]. The kinetodesma is probably an asym- 

 metrical structure. Its relation to the kinetosomes is not 

 yet clear. 



'After encystment, the ciliate undergoes a detorsion ac- 

 companied by an elongation of the rows a, x, y, z, which is 

 essentially due to rapid divisions of the kinetosomes. 



But, whereas in the row^s x, y, z the kinetosomes remain 

 in line, the kinetosomes of a divide tow^ards their left. 

 These granules become lined in a new row h. 



It is clear enough that the course and the length of the 

 rows depend on the phase of the life cycle. 



It is clear also that the division of kinetosomes is induced 

 by some changes in the underlying cytoplasm. The sim- 

 plest hypothesis is, for the time being, that growth of the 

 kinetosomes and their subsequent division depend on the 

 presence of some specific foodstuffs. We may consider also 

 the hypothesis that, when kinetosomes are too numerous to 

 be lined in one row, they invade the adjacent space where 

 they form new lines. All these interpretations wull be con- 

 sidered later on. 



