388 W. CECIL BOSANQUET. 



Sp. anodontfe I am inclined to agree with Schellack, who 

 holds that the appearance which has been thus interpreted 

 is an artifact, due to splitting o£ periplast, since I found 

 that the better my preparations were fixed, the fewer were 

 the examples of this condition. It was found almost invari- 

 ably in films dried in the air (fig. 1), but very exceptionally 

 in those fixed in osmic vapour. It seems possible that the 

 periplast, if it is so to be called, adheres to the slide in the 

 position in which death of the spirochaste occurs, and that 

 subsequently the protoplasm of the organism shrinks and 

 thus straightens its outline a little, leaving a line of periplast 

 following a different line from that finally adopted. At 

 other times the periplast seems to shrink most and to form a 

 band uniting the cells of the spirochaste (fig. 2). 



I have seen a considerable number of specimens which 

 exhibit a dark line running along one side (figs. 3, 4). This 

 probably corresponds with the " crest ^' described by Gross. 

 Judging from the illustrations of spirochastes in section 

 given by him and previously by Fantham, it would seem that 

 the organism possesses a sheath which is loose enough to 

 form a fold along one side in certain conditions. The 

 sheath or periplast stains more darkly than the body-sub- 

 stance of the spirochaete, and hence the double layer appears 

 as a dark line. Splitting of the sheath into fibrillae seems 

 sometimes to occur, as in fig. 6. 



On the other hand, I find it difficult to agree with Schellack 

 that two separate species of spirochaste are present together 

 in Anodouta, one having blunt (figs. 1, 3, 4) and the other 

 sharp extremities (figs. 7, 8, 9). The amount of difference 

 seen is scarcely sufficient to suggest a specific differentiation. 

 Further, the great variation in the length aud thickness of 

 the individuals in each class thus formed is such as to nega- 

 tive the possibility of distinguishing species by length, as he 

 further suggests. It is noteworthy that Schellack distinguishes 

 two species of spirochaete in more than one kind of mollusc, 

 and that Gross also describes two, very similarly differentiated, 

 in Pecten jacobaeus. This rather strongly suggests that 



