"jour'nli.'K^Ts™"'] the Economy of Stephanoceros. 243 



of selection of various matters from the general mass, is effected by- 

 organs manifesting great similarity with those of the normal forms, 

 first by an internal belt of cilia situated in the neck (Plate LIT., Figs. 

 2, 3, a, a), springing fi'om two ciliated processes (h, h), seated bilate- 

 rally in the contractile membrane which recedes from the walls of the 

 body immediately beneath the bases of the lobes ; the belt slopes at 

 a considerable inclination, in a ventral direction, to meet and form 

 attachment with bands descending from the two lobes that in their 

 pentagonal disposition face the dorsal lobe (Fig. 2, c). From these 

 processes clear fibres d, run off towards the brain, and are lost in 

 the mass of that most conspicuous object (e). To this belt then is 

 due the vortex that in the funnel acts as the primary process in 

 conveying to the mouth the nutritive matters that have previously 

 been secured and brought within its influence, and is the represen- 

 tative of the second range of cilia in the higher forms. 



Here also we see that the particles do not pass uninterruptedly 

 into the oesophagus ; they are subjected to the same scrutiny that 

 obtains in the higher forms, and this is here effected by similar 

 organs. The dorsal lobe is produced in a free end or tongue (/), pro- 

 jecting considerably into the funnel, its under-surface is abruptly 

 returned forming an "arched cavity" (^),in connection with a per- 

 manent ridge of the oesophageal septum (li). A similar ridge and 

 cavity are seen on the opposite side just below the attachment of the 

 belt with the bands descending from the ventral lobes ; nevertheless 

 these ridges are not continuous, they support the highly contractile 

 septum at four points ; and although I have not been able to detect 

 them after treatment with potash, they represent the four hooked 

 spines whose existence is referred to by Leydig. 



Both the dorsal lobe and the ventral attachment of the belt 

 create a considerable departure from a true cylindrical form at the 

 neck, the dorsal lobe forming a gap in the collar, apparently to 

 accommodate the incessant working of the tongue beneath, which is 

 actively intruded on the approach of the more minute Infusorial 

 particles which at times are retained in the cavity for periods of 

 varying duration, and at others either swallowed or rejected on the 

 slightest contact, apparently not requiring such careful scrutiny. 

 In the act of swallowing, the tongue approaches simultaneously 

 with the ventral projections, and in conjunction thus direct the par- 

 ticles to the orifice of the mouth, which is protruded to meet those 

 projections and to pass it with that gulping action through the oeso- 

 phagus on to the manducatory apparatus. 



Gosse has evidently taken an " artist's licence " in representing 

 three teeth in the detached figures of the nucus of this organ in 

 Stephanoceros. The laws of geometrical projection show at a glance 

 that these figures are hypothetical and do not represent the same 

 things shown by the figure of the dorsal aspect of the jaws in the 



B 2 



