10 NOCTILUCA MILIARIS. 



vacuoles of more or less size, which have been considered by early 

 writers, as Krohn and Suriray, to be veritable stomachs. These 

 vacuoles are by no means synonymous with the shifting vacuoles 

 of the Infusoria and Rhizopoda. Huxley's idea is that the oral 

 cavity ends in a definite stomach capable of great dilation locally, 

 and these dilations are connected by very narrow pedicles with the 

 central cavity, such giving the appearance of " independent 

 vacuoles." Brightwell's idea is that these " vacuoles," or vesicles, 

 are temporary stomachs, or sacs, formed in the sarcode mass as they 

 are required for the reception and digestion of food, and that they 

 cease to exist after the food is digested. More recent investiga- 

 tions have shown that the food drawn into the mouth is received 

 into the protoplasmic mass at the bottom of the oesophagus ; 

 extensions of this are formed which envelop the food with a filmy 

 surrounding quite distinct from the protoplasmic mass. By this 

 means we have " digestive vesicles " formed. These, however, 

 soon pass into the arms of the central mass till they are sur- 

 rounded completely by the protoplasm. The number of the 

 vesicles vary from four to even twelve, and their place is subject 

 to constant change through the movement of the substance in 

 which they are embedded. The reticulations round the central 

 mass are constantly changing, and thus the distribution of the 

 nutrient material takes place as it finds its way into this network, 

 through the walls of the digestive vesicles. Their contents are 

 found to be principally Algje and Diatoms. That singular diatom, 

 R/iizosole?iia styliforiiiis, was found first of all in the Noctiluca, 

 though it has been since seen floating in large masses on the 

 surface of the sea ; the chief form of Diatom, however, found in 

 this Rhizopod is Adijiocyclus undulatus. As the Noctiluca is so 

 transparent, the form of the Diatom may be seen at a glance. 

 After it has been in the vescicle for a few days it disappears 

 altogether; probably the endochrome has been digested, and the 

 siliceous frustule subsequently rejected. 



The principal agent employed in conveying the food into the 

 aperture, which does duty for a mouth, is a very delicate filament, 

 or " flagellum," similar in character to a cilium, of the Rotifer 

 type, which vibrates rapidly, and is as rapidly withdrawn inside. 

 This band-like organ gradually narrows towards its extremity, and 



