244 Observations on some points in ["j^u^nai. May°f'i?7of^ 



illustrations to his elaborate paper " On the Manducatory Organs 

 of the class JRotifera, communicated to the Eoyal Society in 1856." 

 There are only two teeth to each nucus, the ventral being much 

 stronger than the dorsal tooth. They are thickened near their 

 points, where they give attachment to membranes that connect the 

 one tooth with the other, and form a kind of frame, hinged by one 

 corner to one of the pair of members forming a rudimentary ramus, 

 which also works on what must be accepted as a bona fide fulcrum ; 

 these together permit of a combined backward and lateral move- 

 ment. The malleus is very distinct in the living animal, but 

 vanishes beyond recognition on the application of a weak solution 

 of potash, and the whole apparatus takes a skeleton appearance, the 

 several parts at once forsaking their normal positions under such 

 treatment, and hence the difficulty in arriving at its true character 

 (Fig. 10). 



We now come to a consideration of the visual organs, and when 

 we find that all the facts which natural and physical science have 

 made us acquainted with go to prove that hght is absolutely neces- 

 sary to organization, we may fairly assume that the development of 

 the functional organs of animals requires in some way the influence 

 of the solar rays, even in these minute forms, when we find them 

 possessing orgaus eminently calculated to supply it, though not 

 necessarily to ensui-e the perception of objects ; and though the eyes 

 of the Botifera have received much attention, have been admitted 

 to possess a refracting medium, and to be placed immediately above 

 the homologue of the brain, the tendency hitherto has been to re- 

 pudiate Ehrenberg's acceptance of them as characteristics, and to 

 assign to them only a secondary rank as such, on account of the 

 assumed " curious fact " of their disappearance in the adult stage of 

 certain species. 



Steplianoceros is universally understood to possess only one eye 

 in the adult stage after having had two, both in the ova and young ; 

 even the careful observations of Gosse led him to suppose that the 

 two eyes of the newly-hatched young became by coalescence changed 

 into one in the adult. This is certainly not the case, they do not 

 coalesce, or become changed by any phase of metamorphosis from 

 their normal condition of two to a single eye ; they all possess two 

 eyes. I have during the last nine months examined some hundreds 

 of adult specimens, and have found, without exception, two eyes. 



The adult eyes are easily recognizable with the Wenham para- 

 bola, in a dorsal aspect, and with a little careful focussing in almost 

 any other — at least as far as the red pigment spot is concerned, they 

 require a different illumination to resolve the details. They are 

 seated, not immediately above, uor like a wart upon it, but one on 

 each side of the train, a little below its anterior surface, as seen in 

 a dorsal aspect (Plate LII., Fig. 1), generally in the same horizontal 



