SPIROCHJETID^ 



437 



points out that the strongest arguments in favour of their being 

 bacteria are:— 



1. Diffuse character of nucleus somewhat like Bacillus butschilii, 



2. The possible occurrence of transverse fission. 



3. The absence of a typical kinetonucleus. 



While the points in favour of their belonging to the protozoa are : — 



1. The possession of an undulating membrane. 



2. The occurrence of longitudinal division (denied by Schellach). 



3. The non-plasmolysis. 



4. Difficulty to find artificial media on which they can grow. 



We consider that they are protozoa, and, further, that they are 

 related to the trypanosomes. Spirochsetes are, however, distinctly 

 peculiar, particularly with regard to their diffuse nucleus; but 

 there appears to be almost a series from the diffuse nucleus of the 

 bacteria through the achromatic spiral, with its attached chromo- 

 somes of the spirochsetes, to the condensed nucleus of the higher 

 protozoa. Schellach derives them phylogenetically from the oscilla- 

 tory cyanophees, genus Spirulina. 



Morphology. — Spirochsetes vary much in size, from Spiroschau- 

 dinnia recurrentis, which is 8 in length, to Cristispira halhianii, 

 which may be 150 ijl in length and 2 to 3 /t in thickness. The type 

 species Spirochceta plicatilis Was found in muddy water by Ehren- 

 berg in 1833, and was said by Schaudinn in 1905 to possess an 

 undulating membrane. Sambon, however, considers that this so- 

 called type species is quite different from 5. recurrentis, and should be 

 placed in a different group therefrom. The most carefully studied 

 types are Cristispira halhianii Certes, 1882, found in oysters, and 

 Cristispira anodontcB Keysselitz, 1906, emended Schellach, 1909, both 

 of which have been the subject of research by Fantham, whose results 

 are here followed. These organisms are long, wavy, and thread- 

 like, composed of cytoplasm, which can be differentiated into an 

 ectoplasm, which is generally converted into a thin, flexible, chitin- 

 ous membrane, the periplast. This is continued laterally into a 

 spirally arranged membrane, the crista, containing longitudinally 

 arranged fibrillse, and having a thickened border composed of 

 chromatin. The longitudinal fibrillas are composed of eight to nine 

 principal and numerous secondary fibrillse, which are contractile, 

 and are called ' the myoneme fibrillae ' (Fig. 124). The membrane, 

 or crista, which does not markedly undulate, helps in locomotion, 

 which is rapid, and takes place by a wave-like flexion of the body, 

 which causes forward movement, and a corkscrew motion, produced 

 by the spiral winding of the membrane, enabling the parasite to bore 

 its way through the debris amidst which it may be living. A spiro- 

 chsete can move backwards or forwards indifferently. 



The endoplasm is slightly more granular than the ectoplasm, and 

 contains a diffuse nucleus, which appears to consist of an achromatic 

 filament with bars of chromatin. 



: In addition to this nucleus there is a dot of chromatin (basal 

 granules) at each end of the periplast in C halhianii, and only at one 



