8G THE EOTIFEEA. 



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

 and can bo easily placed in a live-trough without injury ; so that during 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 

 1 1 1 1 -. 1 1 \ and Dr. Leydig. It has, in consequence, been very thoroughly examined, 

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

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

 rest of its internal organisation, as well as the general plan of the coroua, 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 Gonoohilus volvox, and further investigation 

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



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

 cup beneath the chin, just as in M. ringens ; and below this cup, underneath the surface, 

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

 of Bracliionus." 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 trunk. 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 nervous ganglion hi a unique 

 position. All the known nervous ganglia in the Kotifera 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 in the foot. Besides, in 

 the only one of the Melicertadce (viz. Gonochilus) in which there is an obvious nervous 

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

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

 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 in November 

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

 Fig. lc gives a side view of it. It has a conical head fringed with a wreath 

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

 strong longitudinal muscles for withdrawing the corona into the trunk, 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 threads to 

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

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



Length. About T V inch ; diameter of large cluster, about \ inch. Habitat. On 

 water-weeds : common. 



Genus MEGALOTROCHA, Ehrcnbera. 



GEN. GIL Cluster fixed, of many individuals without tubes ; corona kidney-shaped, 

 oblique, with its shorter axis placed dorso-vent rally, and tvith a deep ventral sinus ; 

 dorsal gap in the ciliary wreath very minute ; trunk with four opaque warts in a row 

 on the breast; dorsal and ventral antennae absent.* 



1 Possibly they may be very minute setigerous pimples, which have escaped observation. 



