86 THE EOTIFEEA. 



Tlie cluster is a lovely microscopic object for a low power with dark-field illumination, 

 and can be easily placed in a live-trough without injury ; so that diu-iug the hundred 

 and thirty years which have elapsed since its discovery, it has naturally attracted the 

 attention of many observers, and has been the subject of special essays by Professor 

 Huxley and Dr. Leydig. It has, in consequence, been very thoroughly examined, 

 and only a few pomts of its structure remain as yet doubtful. These, as might have been 

 expected, are in the vascular and nervous systems ; and these alone requhe notice, as the 

 rest of its internal organisation, as well as the general plan of the corona, ciliary wreath, 

 chin and buccal funnel, follows very closely that of M. ringens. 



The Vascular System. — Professor Huxley describes the two lateral canals as arising 

 from a common origin upon the dorsal side of the intestine (rectum), but Dr. Leydig 

 says that the lateral canals start from a common branch opening into a contractile 

 vesicle, which discharges itself into the cloaca : it will be seen that a similar doubt exists 

 concerning the termination of the canals in Conochilus volvox, and further investigation 

 is, I think, wanted to make the matter clear. 



The Nervous System. — Professor Huxley (loc. cit.) describes and figures a ciUated 

 cup beneath the chm, just as m M. ringens ; and below this cup, xmderneath the sm-faee, 

 on the ventral side, a " bi-lobcd homogeneous mass resembling in appearance the ganglion 

 oi Bracliioiius." This organ he supposes to be the true nervous ganglion. Dr. Leydig, 

 on the other hand, points out two nucleated polar cells, giving off threads, just below 

 the mastax, and two similar ones at the junction of the foot and tnmk. These four 

 are, in his opinion, the nerve centres of L. socialis. Now, each of these suppositions 

 is liable to the same objection, viz. that it places the ners'ous ganglion m a unique 

 position. All the known nervous ganglia in the Eotifera lie towards the dorsal surface, 

 and the great majority are near the mastax, and not far from the eyes ; there are no 

 other examples of nervous ganglia on the ventral surface, or m the foot. Besides, in 

 the only one of the MelicertadcB (viz. Conochil'us) in which there is an obvious nervous 

 ganglion, it lies in the normal position ; and M. Joliet describes the nervous gangHon 

 of M. ringens as being above the mastax towards the dorsal surface. No antennas 

 have as yet been observed, and the eyes are visible only in the young. 



The Male. — I had the good fortune to discover and study the male m November 

 1874, and published (loc. cit.) an account of it, and several other males, soon afterwards. 

 Fig. Ic gives a side view of it. It has a conical head frmged with a wreath 

 of long cilia, a cylindrical soft tnmk, and a short, pointed, ciliated foot. There are 

 strong longitudinal muscles for withdrawing the corona into the trmik, and several 

 transverse muscular bands in the integument. The nutritive system is wholly absent. 

 Two secreting foot glands are present, as well as the lateral canals and their vibratile 

 tags. I several times thought I caught sight of the edge of the contractile vesicle behind 

 the upper part of the sperm-sac. There is a large nervous ganglion sending tln-eads to 

 a dorsal antenna and two red eyes. A large sperm-sac fills nearly the whole tnmk, and 

 ends in a broad tubular, ciliated, and protusilo penis. 



Length. About jV inch ; diameter of large cluster, about | inch. Habitat. On 

 water- weeds : common. 



Genus MEGALOTEOCHA, Ehrenberg. 



GEN. GH. Cluster fi.xed, of many individuals without tubes ; corona kidney -shaped, 

 oblique, with its shorter axis placed dorso-ventraUy, and with a deep ventral sinus; 

 dorsal gap in the ciliary wreath very minute ; trunk tcith four opaqtie warts in a row 

 oil the breast ; dorsal and ventral antennae absent.^ 



' Possibly they may be very minute setigerous pimples, whicli have escapcit observation. 



