l8 SPIROCILETES. 



resembling strips of ribbon rather than threads of cot- 

 ton in form. They are further stated to be furnished 

 with an undulating membrane and with a complicated 

 nuclear apparatus (see Figs, i, 2, 3). 



Shape. The length of these organisms is usually 

 not less than twenty times the breadth, Sp. balbianii 

 for example reaching a length of TOO/*, while its breadth 

 is usually less than 5/1. The length of Sp. plicatilis may 

 reach 500^. I have found specimens of Sp. anodontcs 

 nearly 130;* in length, without any signs of division at 

 any point ; but unusually long forms are regarded by 

 some writers as about to enter upon the process of fission. 

 It is difficult to ascertain whether these organisms 

 are naturally flattened in form, as during active move- 

 ment, while they are alive, the exact contour cannot be 

 made out, while some flattening might easily take place 

 after death in the process of fixing. Sp. balbianii is 

 said by Perrin to be round in section. 

 Fantham and Gross have succeeded in 

 obtaining transverse sections of spiro- 

 Cn3etes > which suggest a form such as that 

 chaete in trans- shown diagrammatically in figure 4 a 



verse section. .. , . . , .. , , 



rounded organism with a loose sheath 

 which may project on one side. The organism might 

 thus appear flattened in one direction, and round in 

 another; and the opposing views might thus be har- 

 monised. Gross regards the projecting portion as con- 

 stituting a crest or comb. 



The ends of the organism may be either blunt or 

 pointed (Figs. 2, 3). It is uncertain whether this fea- 

 ture is always constant in the same species. Thus, in 

 the case of Sp. anodonta Schellack would constitute the 

 individuals with pointed ends 1 a separate species (Sp. 



*Cf. Castellani's distinction of Sp.obtusa and Sp. acuminata, 

 page 113. 



