14 SPIROCILETES. 



these, doubt has recently been thrown on the identity 

 of the appearance seen in spirochaetes with the true 

 undulating membrane of such organisms as trypano- 

 somes. Consequently it is premature to regard this as 

 a distinctive feature. Flagella have been described in 

 some of the smaller spirochaetes, but with doubtful 

 certitude ; they appear to be absent in the larger forms. 

 Such absence does not seem to constitute an argument 

 for or against their vegetable nature. The method of 

 reproduction even in the larger spirochaetes is still dis- 

 puted, but there appears to be a balance of authority 

 in favour of longitudinal division as the usual occurence, 

 and I have myself seen an instance of what appeared to 

 be this procedure in Sp. anodonta. l The occurrence of 

 encysted forms in such species as Sp. balbianii has also 

 been held to prove them to be protozoa, but the real 

 nature of the curled up forms is as yet uncertain, and 

 it is not unknown for vegetable organisms to enter upon 

 a resting stage. 



The strongest argument which could be brought for- 

 ward in favour of the animal nature of the spirochaetes 

 would be the occurrence of conjugation a distinctive 

 protozoan characteristic. This phenomenon has been 

 described as occurring in several species of spirochaetes 

 (see p. 37), but the evidence adduced is unconvincing. 



The nature of the smaller spirochaetes is still more un- 

 certain. The points about them which seem to place 

 them in the same class as the larger spirochaetes are 

 their general shape and movements, the occurrence of 

 longitudinal division, the asserted possession by some of 

 them (not by all) of an undulating membrane, and the 

 absence of flagella. Their resemblance to the larger 

 forms in the matter of general shape and movements is 



1 If Schmeidlechner's observation of bacilli which divide lon- 

 gitudinally is confirmed, this mode of multiplication cannot be 

 considered a distinguishing feature of animal organisms. 



