﻿344 CONTRIBUTIONS TO THE NATURAL HISTORY 



li°-ht upon the structure and functions of the whole apparatus. Let us, for this pur- 

 pose, go back to a renewed consideration of the funnel itself. We have seen that 

 it is simply a central, vertical, downward prolongation of the main central cavity, 

 tapering gradually into a narrow neck (Plate III. Fig. 1 and 2) ; but before it reaches 

 the lower surface, it enlarges again very suddenly, branching into two forks, which 

 are themselves swollen into two irregular bulbs resting against the lower surface, one 

 in front, and the other behind the central black speck, but both close to it, and 

 partly encircling the tubercle upon which the black speck rests. These two bulbs are 

 therefore simply dilatations of the forked lower extremity of the funnel, and we con- 

 stantly see undigested matters accumulated in them and revolving in their cavity, with 

 a tendency to accumulate laterally in an obliquely opposite direction in each of them. 

 And at long intervals these prominent oblique angles will open (Plate V. Fig. 9), when 

 the fecal matter within the bulbs is discharged, the aperture remaining for a longer or 

 shorter time extended, and the vibrating cilia lining the inner surface playing very ac- 

 tively ; but after a little while, these openings shut again. 



These apertures might, therefore, be considered as a double anus ; but I think it were 

 a very injudicious comparison to homologize them with the anus of higher animals, for 

 in this type the process of digestion and assimilation, and the circulation of the nutritive 

 digested food, are carried on by means of apparatus widely different from what we ob- 

 serve in either Mollusca, Articulata, or Vertebrata. We have seen above, that the 

 food is introduced into the digestive sac which hangs into the central cavity ; that this 

 sac opens freely into that cavity, and discharges there its contents, mixed with a large 

 quantity of water ; that this peculiar apparatus is subject to regular contractions, and 

 circulates the fluid, with the nutritive parts suspended in it, into the various tubes branch- 

 ing through the whole system, and that gradually the refuse matters drop into the central 

 vertical funnel, to be discharged below through the openings of the two hollow bulbs 

 branching from its lower extremity. We have here, therefore, rather openings in the 

 circulatory system than anal apertures, or rather, we have here an apparatus entirely 

 different in its adaptation from either the alimentary canal or the circulatory system of 

 higher animals, but constructed upon the same plan as similar apparatus in the class of 

 Polypi and in other Medusse, with only this difference, that in Polypi the digestive 

 central sac empties its contents into a large cavity subdivided only with partitions, with- 

 out definite circulatory tubes, but along which the fluids are nevertheless circulated up 

 and down, and into the tentacles, and discharged either in a retrograde current through 

 the stomach and mouth, or through the tentacles and lateral pores, when such exist. 

 In Discoid Medusae a similar circulation takes place, but without openings either in 



