92 NOTES AND MEMORANDA. 



cilia tbero are two distinct groups of Oxi/trlchina, or rather two extreme 

 modifications with intermediate forms. In one of these, including 

 Oxytrlcha, StylonicMa, &c., the cilia are greatly differentiated both as 

 to form and function, and limited in number : in the other ( Uroleptus, 

 IJrostyla) there are two rows and upwards on ventral cilia, each row 

 containing an indefinite number. A new genus and species, Tricho- 

 gaster pilosus, is interesting from the fact that it is the lowest known 

 form of Oxytrichina, its cilia presenting the smallest amount of 

 differentiation. 



For the sake of clearness, the author proposes to distinguish by 

 numbers the eight characteristic frontal cilia of StylonicMa, Oxytricha, 

 Histrio (nov. gen.), PleurutricJia, and AUotricha (nov. gen.). The 

 dorsal cilia are not, as Stein thought, young marginal cilia. They 

 occur over the whole dorsal surface in longitudinal rows, each row 

 being set in a distinct furrow. They exhibit little movement, and 

 are differently constructed to the other cilia, being mere cuticular 

 processes, containing but little protoplasm. They may be absent. 



5. Transverse Division. — A very exact account is given of the 

 development of the new cilia of the two daughter-individuals arising 

 by a process of transverse division. According to Stein, the new 

 marginal cilia arise as a single longitudinal row on each side, which 

 subsequently divides : but according to Sterki this account is incorrect. 

 He states, in fact, that the mode of origin of the marginal cilia is 

 different on the right and left sides, and takes place as follows : — On 

 the right side the row of marginal cilia of the parent splits up into 

 three groups, enclosing two intervals, in each of which appear fine 

 close-set cilia. These arise somewhat nearer the margin than the 

 old cilia, and, as development goes on, they get further and further 

 from one another, the rows themselves, at the same time, approaching. 

 The old cilia simultaneously undergo absorption, although young in- 

 dividuals are often met with which have some of the maternal cilia 

 left. On the left side the parental marginal cilia split up into only 

 two groups : in the single interval between them appears one of the 

 new rows, the second making its appearance between the anterior end 

 of the old row and the adoral cilia. A further difference between 

 the two sides is met with in the fact that the new marginal cilia of 

 the left side arise further from the margin than the old ones. 



In StylonicMa, Oxytricha, and Histrio, the frontal, ventral, and 

 anal cilia of each daughter-cell arise from a common group of eighteen 

 cilia, that of the anterior individual being situated to the right of the 

 parent peristome, that of the posterior individual to the right of the 

 new peristome. Each group consists of six oblique rows, containing 

 1, 3, 3, 3, 4, 4, cilia respectively, counting from left to right. Of these 

 the single cilium of the first (leftmost) row, the two anterior cilia of the 

 second and third rows, and the three anterior of the sixth, become the 

 eight frontal cilia ; the two anterior cilia of the fourth, and the three 

 anterior of the fifth row, become the five ventral cilia ; while the 

 posterior cilium of each row except the first becomes one of the five 

 anal cilia. 



During division, the anterior or old peristome alters its form. 



