164 CTENOPHOR^. Part II. 



final course, circulate the cliymiferous fluid with which they are filled into all parts 

 of the spherosome ; and there is this remarkable peculiarity in the general current 

 ot this chyme circulation, that the fluid contained in one half of the body, reversing 

 regularly its covu'se, is alternately poured into the opposite half and back again. 

 Thus the chief peculiarity of the cliymiferous system of the Ctenophora? does not 

 only consist in its bilateral syuimetr\-, but also in the antagonism of the ciu'- 

 rents of its two lateral halves. 



Next, we have to notice the vertical prolongation of the cliymiferous system 

 in the shape of a funnel, extending to the abactinal pole of the body, in the 

 prolongation of the main axis, and there, dividing into two forks, running to some 

 distance in opposite directions, between the anterior and posterior pairs of locomotive 

 flappers. The fork of this funnel forms a sort of cloaca, in which the refuse of 

 the cliymiferous fluid accumulates, to be at intervals discharged through two distinct 

 openings, placed o))li(|uely on opposite sides of the circumscribed area of the 

 abactinal pole. The physiological significance of the circumscribed area has not 

 yet been ascertained. It is an elongated field, circumscribed by a more or less 

 prominent wall of A'iljratile fringes, interrupted in the middle by a j^rominent organ, 

 considered to be an organ of hearing by some anatomists, and described by others 

 as an eye-speck, towards which convei'ge the abactinal prolongations of the rows 

 of locomotive flappers. 



One of the most apparent peculiarities of the Ctenophor*, and to which this 

 order of Acalephs owes its name, consists of eight rows of locomotive flappers, 

 extending along the eight vertical and peripheric cliymiferous tuljes, with which 

 they are closely connected. As far as I can ascertain, all Ctenopliora3 have eight 

 such rows, though some of them are represented wdth only four and others with 

 twelve. But their close connection with the ambulacral tubes, and the constancy of 

 the number of these tubes in all the Ctenophorto wdiich I ever had an opportunity 

 of examining, lead me to take it for granted that the typical number of the 

 vertical rows of locomotive flappers must be eight. I am inclined to ascribe the 

 conflicting statements upon this point to the marked inequality observed among these 

 rows in different families. The fact is that while they are, all eight, of equal 

 length and equal prominence in certain representatives of this order, in others 

 there are four larger, longer, and more prominent ones, and four shorter and 

 smaller ones, differing more or less in their course. I hold, therefore, that the 

 smaller rows may have been overlooked in those genera which are described as 

 having only lour rows of locomotive flajjpers ; and that, in those which are repre- 

 sented as having twelve rows, the vibratile cilia of the epithelial cells lining the 

 digestive cavity may have been mistaken for additional rows of locomotive flappers. 

 Gegenbaur gives the same explanation of the singular figure of the Alcinoe 



