102 THE ROTIFERA. 



In general, the species cannot be discriminated, while in life and activity, without 

 extreme difficulty ; their differences are so very slight, their dimensions so minute, and 

 their restlessness so incessant. P.H.G.] 



C. DEFLEXUS, Ehrenberg. 



(PI. XXVI. fig. 1.) 

 Colurus deflexus . . . Ehrenberg, Die Infiis. 1838, p. 476, Taf. lix. fig. 9. 



[SP. CH. Lorica, viewed dorsally, broadly ovate, bluntly pointed before, produced 

 behind into two acute spines, separated by a wide, deep sinus : viewed laterally, the 

 outline is the quadrant of an oval : the venter cleft from end to end ; foot robust, with 

 two short, slender, acute toes. 



If I rightly identify the species, there is little difference of aspect between this and 

 bicuspidatus. In this the posterior spines are said to point slightly below, in the other 

 slightly above, the horizontal line. Yet as this depends on the angle at which the 

 animal is viewed, which is every instant varying, the distinction is evanescent, and, I 

 fear, worthless. Yet, on careful study, this, which is by much the more robust species, is 

 seen to have the two halves of the lorica severed all round, except in the middle of the 

 back. The fore edges of these halves, deeply truncate, but a little out-curved, are firmly 

 pressed together in retraction ; and the effect of this appression, when seen from above, 

 is the dividing line of the blunt cone, which is seen minutely opening and closing every 

 moment. A muscle-band passes, in relaxed curves, from the front of each of the appressed 

 sides to the surfaces of the retracted organs seen in a confused heap far down, evidently 

 for the purpose of pulling out the trochal apparatus when required. 



A large pale crimson eye seated on an ample brain-sac ; a mastax of the Euchla- 

 nidan pattern ; a cylindrical stomach succeeded by a wide intestine ; an ovary often 

 containing a nearly developed egg ; and a small contractile vesicle ; are usually seen. But 

 in the middle of the back, just under the lorica, are two curious organs, each apparently 

 an agglomeration of minute, clear vesicles, perhaps of air, perhaps of oil, observed long 

 ago by Ehrenberg. He declared them inexplicable ; and I cannot supply the explanation. 



When, after a self- inflicted imprisonment, it may be of hours, the Colurus opens its 

 closed cheek-plates, a trochal mass of conglobate lobes, fringed with wreaths of cilia, is 

 thrust out, by whose vibration the creature smoothly but rapidly shoots away. The 

 frontal hooked-plate, which, even in the inert state, has been discernible by the delicate, 

 thin, curved line of its edge, moves to and fro, and under very favourable circumstances 

 we may see that its inferior surface is fringed with vibratile cilia. I judge it to be an 

 organ of touch ; Herr Eckstein's opinion to the contrary notwithstanding. P.H.Gr.] 



Length. Of lorica, ^ rn - inch ; from hook to toes, 1 j^ inch. Habitat. Ponds and 

 ditches ; quite common (P.H.G.). 



C. BICUSPIDATUS, Ehrenberg. 



(PL XXVI. fig. 2.) 

 Colurus bicuspidatus . . Ehrenberg, Die In/us. 1838, p. 476, Taf. lix. fig. 7. 



[SP. CH. Almost exactly those of C. deflexus, except that the lorica is not cleft 

 either dorsally or ventrally ; but only excavate behind, slightly on the dorsal, deeply on 

 the ventral side. 



I have seen only a few examples of this form, all from Button Park, Birmingham. 

 It is, I presume, Ehrenberg's bicuspidatus, his figures showing a lorica undivided 

 beneath. In examples long under examination, I became quite certain that neither the 

 dorsum nor the venter was cleft ; but a narrow sinus, reaching to more than one-third 

 of the lorica in length was excavated up the flat ventral plate, and a very slight one out 

 of the dorsal end. Through this orifice the foot is thrust, of rapidly diminishing joints, 



