PHYSIOLOGICAL CHARACTERISTICS OF AXIATE PATTERNS 95 



moves backward almost as frequently as forward; consequently, the possi- 

 bility suggests itself that this secondary gradient, evident only in some in- 

 dividuals of a lot, may, like the reversed oxidation gradient of Paramecium 

 (p. 91), be associated with frequent backward locomotion. Cytolysis of 

 Stent or coeruleiis in cyanide progresses over the body in a wave from the 

 peristome, and in VorticeUa and Carchesium the differential in the body is 

 similar. The contractile stalks of these animals, however, show evidence 

 of specific susceptibility to certain agents. According to Merton (1929), 

 their susceptibility to formol is less than that of the peristomial cilia, but 

 greater to lactic acid, pilocarpin, and alcohol; indications of specific sus- 

 ceptibility of the contractile fiber of the stalk in these forms have also been 

 observed with other agents (Child) . This fiber, capable of extremely rapid 

 contraction, undoubtedly is a highly differentiated part of the cell; it is 

 not surprising, therefore, to find it specifically susceptible to particular 

 agents. All hypotrichous ciliates examined for differential susceptibility, 

 with one exception,-^ showed anteroposterior gradient. Anteroposterior 

 susceptibility and indophenol gradients were observed in a Monocystis 

 from a marine poly clad. 



The susceptibility gradient of holotrichous, heterotrichous, and hypo- 

 trichous ciliates is evident, not only in change of form and cytolysis but 

 also in retardation and cessation of ciliary movement, which progresses 

 from the anterior end posteriorly, except in those individuals which show 

 a posteroanterior gradient in the posterior region ; in these this gradient 

 appeared in the cilia. 



The evidence for the existence of a gradient pattern in axiate protozoa 

 has been presented in considerable detail because presence in the morpho- 

 logically differentiated part of a single cell of a spatial physiological pat- 

 tern showing essentially the same characteristics as are found along the 

 axes of multicellular animals, at least during earlier developmental stages 

 and often throughout life, is significant as indicating that organismic pat- 

 tern is independent of cell boundaries. The same physiological features of 

 pattern appear within the single cell and in the individual consisting of 

 millions of cells. That an axiate, or, more strictly speaking, polar, proto- 

 zoan pattern consists only of these gradients in the fully developed animal 

 is certainly far from true, but that they are essential factors in the develop- 



5 Siylonychia, Oxytricha, Onychodromits, Kerona, and Euplotes all show an anteroposterior 

 ectoplasmic gradient. In a Japanese species somewhat similar to Uronychia a posteroanterior 

 gradient was observed. Whether this is associated with the very large and highly developed 

 posterior cirri, as seems probable, or with some other factor could not be determined, since 

 only a few individuals were found and since attempts at cultivation were not successful. 



