88 THE ROTIFER A. 



* Genus TROCHOSPH.ERA, Semper. 



GEN. CH. Solitary, free-swimming ; body a perfect sphere; buccal orifice on the 



spherical surface; principal wreath dividing the sphere into tivo hemispheres, and pass- 

 ing above the buccal orifice; dorsal gap in the wreath at the pole opposite to buccal 

 orifice; secondary wreath a fragment on the under edge of the buccal orifice ; ventral 

 antennse extremely minute; tube absent. 



T. iEQUATOEiALis, Semper. 



(PI. D. fig. 11.) 



Trocliospluera ceguatorialis . . Semper, Sieb. u. Kiill. Zeits. Bd. xxii. 1872, p. 311, Taf. 



xxiv., translated in Mon. Mkr. J. vol. xiv. 1875, 

 p. 237, pis. cxx. to exxii. 



Who can complain here that a rough wrinkled skin, complicated external form, and 

 huddled-up organs have rendered his utmost efforts almost fruitless ? Here is a creature 

 whose outer shape and texture have alike reached the very acme of simplicity ; the one 

 translucent as the clearest water, the other rounded into a perfect sphere : an 

 animal created as it were for the study of its internal structure ; its organs all sym- 

 metrically spread apart in due array, just as if a skilful demonstrator had teased them 

 out with delicate needles ; no one overlapping another, and all deftly hung to the walls 

 of a hyaline globe which not only upholds them, but also displays them to the utmost 

 possible advantage ; for it has a band of cilia girdling its entire circumference, and 

 rolling it through the water, so as to present it in every possible point of view. 



Trochosphara has a perfectly transparent spherical body with a principal ciliary 

 wreath running round what may be called the equator, and marking the common 

 boundary of what Prof. Semper calls the " oral " and " ab-oral " hemispheres. In the 

 former lie nearly all the organs of the body ; for only one nerve-thread and portions 

 of a pair of muscular bands are to be found in the other. At one spot in the equa- 

 torial ring of cilia there is a break in the wreath, and at the opposite extremity of 

 the diameter passing through this spot is the buccal orifice, which has a very small 

 secondary wreath fringing its oral or lower side. 



The various internal organs are so well displayed in Prof. Semper's figure, that 

 only a few points require notice. The trophi, though of somewhat peculiar shape, are 

 malleo-ramate. The lateral canals end in the cloaca, not in the contractile vesicle ; 

 and this latter, according to Prof. Semper, discharges itself into the intestine. The 

 nervous system can be well made out. From the nervous ganglion (ng), which lies 

 close to the mastax (mx), five pairs of nerves pass respectively to the ciliary wreath, 

 buccal orifice, lateral antennse (a'), lateral canals (Ic), and eyes (e) ; while a single 

 nerve thread («) passes to the probable dorsal antenna (a). 



The male is unknown. 



It is obvious that if the aboral hemisphere were pressed flat, and the oral lengthened 

 out into a cone, we should have, in the altered Trochosphcera, a Rotiferon somewhat re- 

 sembling one of the Melicertadce. For it would have a buccal orifice laterally placed ; a 

 principal ciliary wreath surrounding the body, with a gap in it on what would then be 

 the dorsal side ; a portion of a secondary wreath passing round the edge of the buccal 

 orifice ; tropin of a Melicertan type ; two minute ventral antennse, and a single dorsal one. 

 On the other hand, the absence of an attached foot, and of a complete secondary wreath, 

 and the difference of habit, make it no easy matter to say where Trochosphcera should be 

 placed ; on the whole, I think it should be put among the Melicertada: near Megalotrocha 

 and Gonochilus. 



Length. Diameter of sphere, ^\ inch. Habitat. Ditches in the rice fields of 

 Zamboanga, in the Philippine Islands (Prof. Semper) : rare. 



