ORIGINS OF AGAMIC PATTERNS 617 



a spiral pattern of ciliary beat. Very commonly, however, the morphologi- 

 cal pattern shows a spiral asymmetry, even in forms such as Paramecium, 

 in which there is comparatively little regional morphological differentia- 

 tion; and spiral pattern is often much more conspicuous in the more 

 highly differentiated forms. The pattern of the peristomial cilia and mem- 

 branelles of ciliates is usually spiral, and in many species the whole ecto- 

 plasm apparently possesses spiral pattern. Among the parasitic flagellates 

 remarkable developments of certain types of spiral pattern appear. In 

 the genus Spirotrichonympha, for example, spiral bands at or near the 

 inner surface of the ectoplasm make a series of definite, regularly spaced 

 turns around the body, and the numerous flagella connected with them 

 form corresponding spirals. Of two species, S. polygyra and S. bispira, 

 recently described by Cleveland (1938) with spiral bands extending over 

 some three-fourths of the body length, the former shows forty-five, the 

 latter thirty-four, turns of the bands; and, according to Cleveland's fig- 

 ures, there is little deviation from geometrical regularity in the spacing 

 of successive turns and slope of spiral. In division of S. polygyra the 

 bands unwind, beginning at the anterior end, two going to each daughter 

 individual and two developing anew. In S. bispira a new band without 

 spiral arrangement develops from the point of origin of the parent bands 

 at the anterior end and migrates to the posterior end of the cell, which 

 becomes the anterior end of one of the daughter individuals. There the 

 band gradually becomes spiral, at first not completely regular, beginning 

 at the end originally anterior in the parent cell and now at the new an- 

 terior end of the daughter individual. The second flagellar band develops 

 from the anterior end of the first, extends posteriorly in the new individual, 

 and forms a spiral between the turns of the first band. Various other 

 features of pattern in these species — the axostyle and the elongated cen- 

 trioles — are of interest as indicating a high degree of differentiation, but 

 the description of these remarkable forms and their divisions serves to 

 emphasize the fact that we have not the remotest conception of the physi- 

 ological factors concerned in the origin and development of such pattern, 

 but that it originates and is localized in relation to regional differences in 

 physiological activity with a definite pattern seems evident. 



A dorsiventral, as well as anteroposterior, pattern appears in the Hypo- 

 tricha, together with a great variety of morphological asymmetries in ar- 

 rangement of cirri and membranelles, most of which are genus- and 

 species-specific; but in cell division the asymmetries of daughter individ- 



