ON THE STRUCTURE OF NOCTILUCA MILIARIS _ 355 



" However carefully I have sought for a digestive canal of any- 

 kind, I have never been able to discover anything of the sort ; but I 

 have very frequently seen more or less considerable vacuoles in the 

 midst of this substance. It is these most probably which have been 

 regarded as stomachs by MM. de Blainville and Suriray." 



I have never seen this projecting mass nor any foreign bodies in 

 the position indicated by Quatrefages, in perfectly fresh specimens. 

 In those which had undergone alteration, on the other hand, such an 

 appearance was frequent, but it invariably appeared to me to result 

 from a partial extrusion of the contents of the stomach. 



The appearance of ' vacuoles,' on the other hand, is almost invari- 

 able in fresh specimens ; but I cannot think that these clear spaces, 

 which are defined by a well-marked membranous wall, have any 

 analogy with the shifting ' vacuoles ' of the Infusoria and Rhizopods. 

 It appeared to me, on the other hand, that the oral cavity led directly 

 into a definite stomach, whose walls are capable of very great local 

 dilatation, such dilatations, connected by very narrow pedicles with 

 the central cavity, then having all the appearance of independent 

 vacuoles (fig. 3 e). The accumulation of granules around the central 

 mass greatly contributes to this appearance. Like Krohn, I frequently 

 noticed large Diatomacese and other foreign matters in these gastric 

 pouches. 



Not only does all I have observed lead me to believe that Noctiluca 

 has a definite alimentary cavity, but I am, as I have said above, inclined 

 to think that this cavity has an excretory aperture distinct from the 

 mouth. The funnel-shaped depression in the post-oral area, in fact, 

 always appeared, when I could obtain a favourable view, to be 

 connected with a special process of the stomach. On one occasion 

 I observed the sides of this process to be surrounded by fusiform 

 transversely-striated fibres or folds, I could not determine which. 



Krohn states that he repeatedly saw the egesta voided ' in the 

 neighbourhood of the groove of the body,' but he could not determine 

 at what exact point, and he inclines to think it must have taken place 

 through the mouth. 



I am equally unable to bring forward direct evidence on this point, 

 and my belief in the existence of a distinct anus is founded simply on 

 the structural appearances. 



In front of and above the gastric cavity is the nucleus {c), described 

 by Verhaeghe and Krohn. This is a strongly refracting, oval body of 

 about i-46oth inch in length, which, by the action of acetic acid, 

 assumes the appearance of a hollow vesicle. The anterior radiating 

 fibres pass from it ; the posterior from the alimentary canal. 



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