*j™\ Mrn^Ta''] tlie Economy of Stephanoceros. 245 



plane, but at times very irregularly placed, one eye being far below 

 the other, and almost hid Irom view by the interposition of the 

 granular masses that obtain on each side of the brain (Fig. 1, I, I). 



Their true character is difficult to determine, they resemble in 

 a marked degree the eyes of Vertebrates, consisting of a globe, 

 sending off posteriorily a fibre to the brain, and possessing ante- 

 riorily a pigment spot, which, while favouring the form of the 

 compound type (Fig, 4), contains within itself a central refracting 

 medium ; but whether this be a simple expanding orifice, like the 

 iris (Fig. 7), or annular (Fig. 5), or whether it consist of a number of 

 facets, like the compound eye (Fig. 6), I am somewhat doubtful : 

 these several appearances have, under conditions beyond my appre- 

 ciation, presented themselves, but I believe Fig. 7 to be the true 

 representation ; of this, however, we may be certain, that whether 

 they incline to the simple or compound type, they are eminently 

 calculated to fulfil the purposes they are requu-ed to serve, in simply 

 conveying light, though not the perception of objects to the brain, 

 for they possess no choroid. 



I will take this opportunity of mentioning that, amongst other 

 Rotifers, I find two eyes in the adult Floscularia coronet fa, which 

 at the date of my description* of that species I had failed to notice, 

 owing to the tutored impression under which I then laboured as to 

 their disappearance in the adult stage in the whole genus. 



Stephanoceros manifests a marked resemblance to Lacinularia 

 in the arrangement of the vessels and sacs composing the water 

 vascular system, and in tracing the courses of these vessels up from 

 the region of the cloaca, I came, to my gratification, upon a rudimentary 

 antenna provided with the characteristic bristles, and at once found 

 its companion on the opposite side, each in connection with a pidsatile 

 sac (Plate LII., Fig. 2). From these antennae the vessels send 

 off" anteriorily two branches, one to each of the processes of the 

 ciliated belt (a), thence continuing horizontally and uniting with its 

 fellow at the base of the dorsal lobe ; the other branches run in the 

 direction of the adjacent lobes alongside the brain and anastomose 

 with the horizontal branch ; the vessels each contain a sac, just below 

 the stomach, one at each antenna, one at each of the ciliated processes 

 of the belt, one in each of the vertical, and another in each of the 

 horizontal branches ; that is, five on each side as in Lacinularia. 



I have adopted the term pulsatile sac, in preference to that of 

 vibratile or tremulous tag, from the fact that in Stephanoceros they 

 do not occur as pensile bodies projecting into the body cavity, and 

 are not capable of being swayed about with every movement of the 

 fluid with which the body is filled ; they occur as swellings in the 

 vessels, similar to what Huxley describes in Lacinularia, in which 

 he states the flickering appearance to be produced by " a long cilium 

 * ' M. M. Journ.; Sept. 1860. 



