866 MR. J. E. S. MOOEE ON THE STBTJCTUEAL 



of substance running down the entire length, of each ridge, or in 

 reality an apparently resistant structure which may have much 

 to do with the rapid undulations and contractions of the animal 

 when in activity. Still more interesting in relation to these 

 appearances were a series of sections across the oral furrow from 

 its anterior extremity until it finally dips into the inner sarcode 

 by a distinct ostium (fig. 4). This furrow contains at its bottom 

 a little ridge ; and immediately below this is a dense rod similar 

 to those above, only much larger in section (fig. 6, a). The ridge 

 bears, above, the well-known oral cilia along its whole length, and 

 the rod appears to act as a support for the whole ciliary apparatus. 

 The sarcode is more firmly in connection with the inner edge of 

 this rod than the surrounding parts, and there appear faint re- 

 fractive lines running from this inwards (fig. 6, F). I cannot under- 

 stand the significance of these refractive striae unless the fibrillation 

 represents the agent in transmission of something like a nervous 

 impulse from the inner protoplasm to a specially mobile region. 



When subjected to a precisely similar treatment, the proto- 

 plasmic body of Paramoecium shows no such difi'erentiation 

 into a reticulum of chromatic fibres and achromatic spaces as 

 that described above. Their contents are far more nearly 

 uniformly made up of granular protoplasm imbedded in which. 

 are seen the food-stufi's as more deeply-staining masses. At 

 the same time there do appear about the huge macronuclei 

 irregular spaces and lacunae having no immediate connexion with 

 the contractile vacuole, which are undoubtedly analogous to 

 the more numerous spaces (" Saftkammern ") in Peridinium. 

 Consequently they must be looked upon as all that is left of the 

 splendid protoplasmic network of the Spirostoma. 



The dying out of the necessity of such a reticulum, through 

 forms like Peridinium to the Paramcecia, is a very curious fact, 

 and it shows, I think, that we have not yet done with protoplas- 

 mic reticula, at any rate in the sense of their significance. 



Irregularly disposed throughout all the internal reticula of 

 Spirostomwm are innumerable small refractive dots. They appear 

 along the fibres of the network and become more numerous 

 towards the periphery on all sides (fig. 3). With care they are 

 to be seen in the interior of the living animal, and in sections 

 appear closely connected with the double spiral rows of dots 

 characteristic of the species. I have elsewhere * described the 

 * Ann. & Mag. N. Hist. 6th ser. vol. xi. p. 149. 



